Well as the title says, avast! seems to be affecting my computer in relatively odd way, and to be honest, I didn’t think it was avast! at first since Windows Vista is still known to have its quirks. Anyway, to get into the details, I’ve noticed some peculiar slow-downs in some of my computer’s behaviour, and the only real issues I seem to notice are these three:
1.) Apparently when I stream videos on any website using either browser I have (Firefox is my main, but I’ve tested this with IE7 as well) that use Flash, immediately once the video file is done loading there will be some slight lag. To describe this a bit better, the screen in FireFox will lag for around 0.5-1 seconds then resume normally, or if I were playing the video while it finished, it would suddenly lag/get choppy/slow down for 0.5-1 seconds. I’ve also noticed that when this lag occurs for such a short duration, I hear some intense Hard drive activity that immediately goes away once it’s done. Other lag symptoms similar to this occur when I’m already playing a streaming file but decide to close the tab it’s in or close the window–there will be high HDD activity and a slight delay in shutting that all down.
At first I thought it was an issue with Flash, internet lag or something else on my system, but it turns out that after disabling all the providers on avast! and trying to play the videos again, it ran perfectly smoothly after loading without any hint of the sudden lag issue.
2.) This issue is bit vaguer and could or could not be relevant, although I am a bit suspicious after doing some testing. Basically when I start up my computer, once everything loads up after the whole “Welcome” screen, there is some mild hard drive activity which is normal. Then there was something new I noticed that didn’t occur to my old computer that was similarly configured but ran on XP SP2 where shortly after the hard drive on this computer started having high amounts of activity for a short while (haven’t actually managed to time it).
I believe this is something normal with Vista since regardless of all my tweaking in Vista already (such as making sure no redundant processes are running or are on start-up) there still seems to be some high activity once I start up. Nothing in specific appears to be updating, installing or running, and since I’m not entirely familiar with the intricacies of the computer, my guess is that Windows is probably doing some new form of caching of some sort (seeing as how this still happens even after I disabled features such as system restore and the search indexer). Now the real issue here is that normally this high hard drive activity doesn’t last very long at all after trying a few boot-ups with avast! disabled. However, when avast! is running with all its providers on it will take significantly longer for the high hard drive activity to die down, and this caught my attention and worries me a bit. Is it possibly that this is just normal, or is there some form of glitch that makes avast! perform slower than usual on Vista?
The only relevant information I could really find so far is in this thread which provides no real solution just yet.
3.) This is an older issue that I posted on earlier here but didn’t get a response on. Basically I get a ton of error messages from avast! whenever I try deleting my cache for FireFox when it’s still open through the “Tools->Clear Private Data” option. This also appears when I clear some temporary files and certain Windows files using CCleaner. There’s no notable issue here except the fact that once I click/confirm the action to “Clear Private Data” in FireFox, there is some lag in FireFox’s response for around 0.5-1 seconds before it processes the request, and I’m guessing its here that avast! does something odd. Similarly when running CCleaner, it will run through cleaning fine, but for some unexplainable reason during the process of cleaning the window will sometimes flicker as if it were closed then reopened in fraction of a second (this only occurs in some cases though like after I haven’t cleaned a lot of junk recently, and I can’t entirely confirm that this is a CCleaner problem or a Vista problem since CCleaner runs perfectly on my XP systems, and I haven’t seen any other reports of this happening with CCleaner users on Vista systems).
There is technically a fourth issue I noticed right now, but I’m not even sure if it’s something with avast! or rather an odd conflict issue with FireFox and Vista. Basically just recently when I did some testing with avast! disabled, once I enabled it again and ran FireFox to do some browsing, the websites suddenly stopped responding. So I closed FireFox, then reopened it to find that all my settings for FireFox were reset! (some things were retained, like bookmarks, saved passwords and cookies, etc., but the actual options had to be reconfigured) The odd part about this is that I’ve run several scans before and just afterwards but found nothing on my computer, suggesting that it isn’t something that was malicious. So really I’m not sure if suddenly enabling avast! again was the problem or not, but I thought I’d post here just in case it was relevant in some way or another. Also I’ve done this a few other times but it doesn’t seem to occur again, although the first time this happened was when I restarted the computer with the providers all off (when it booted up again the providers were all back on again and I had to disable them yet again–this could have some relevance).
Anyway that’s about all the information I have so far on the noticeable issues/slow-downs avast! has on my system. Here’s some more information about my computer for reference:
Brief System Specs:
-Windows Vista Home Premium (32-bit, fully patched and now has SP1 which has not changed the problems at all)
-AMD Athlon 64 X2 Dual-Core 6000+ (3.02 ghz each)
-4 GB of RAM
-320 GB of HDD space (with 16 mb cache, and still have over 53% free space)
Security Programs:
-avast! Home Edition (4.7.1098 with Real-time settings put on High)
-Windows Defender (real-time)
-SAS Free Edition 4.0 (on demand)
-Spyware Blaster 4.0
-HiJackThis 2.0.2
-Windows Firewall
Other Programs:
-FireFox 2.0.0.12
-NoScript Plugin (1.4.9.5)
-CCleaner (fully updated)
-Flash plugin for both IE and FireFox (fully updated, version 9)
Some things I tweaked in Vista that may have relevance:
-Turned off Search Indexer
-Turned off System Restore
-Set MS update to manual
-Only start-up processes are the essential normal windows ones, my nvidia video card drivers, MSN messenger, avast!, and windows defender.
-Media Center redundant processes are manually disabled.
-Have done defrags every now and then using the Vista integrated one
-Also no notable malicious behaviour or infections aside from these odd slow downs from avast!
If anyone needs more information or wants me to do some further testing, I’m more than willing to help and will see what I can do about it. Thanks for your time to those who’ve read through this fairly long post! 
Note: avast! already came with this computer when I first got it late last year. Also Windows Vista was already pre-setup with some of the manufacturer’s other programs and I only had to enter in some configuration settings and the CD-key. avast! was also a later version than the ones available (unfortunately I forget which version, but it was still one of the more recent 4.7.x builds), but I stuck with it since I recall one of the newer updates right before 4.7.1098 had some issues with it (was it the 4.7.1043 one? I don’t remember…1043 might actually have been the one I had although again it’s relatively hazy). I’m not sure if this has anything to do with the problem here though, but I thought I should include this bit of information as well.
Now just to clarify things a bit, I don’t enjoy making long pieces of posts like these as they do pose problems. Really all I’m trying to do is contribute the most bit of information I have on this in one area to help diagnose the problem a bit faster.