I have avast running with 4 shields. Sometimes avastsvc cpu usage goes to 90% and stays there. Rebooting the computer doesn’t seem to solve the problem because when I right click on a file the cpu usage jumps right up there again. I have found that it usually occurs when I plug in a USB flash drive and then start to explore the folders in the flash drive. The computer I am running avast on is only about 450 MHZ with 278 MB of ram running XP SP3 with a USB 1.1 interface :'(. Avastsvc cpu usage would go through the roof. This happened a couple of times with 4.8 also. With the USB flash drive plugged in, it would take forever to view the MY Computer window, until I physically unplugged the drive and then avastsvc would settle back down. The only way I can fix it is to do a repair, then avast returns to normal until it happens again. Still think avast is the best freeware in town.
Any other security program that could interfere? Any old antivirus?
Are you running the latest 5.0.418 version of avast?
The only other security program I am running is Rising antivirus with only the HIPS installed. No realtime protection. The only other antivirus installed on this machine was avira and that was a long time ago. Running the latest version. Thanks. The problem is intermittent and when it does occur, a simple repair seems to fix it. Thanks
Hmmm… seems Rising is messing things here.
Or a bad uninstallation of Avira.
After you use Add/Remove, you should use Avira Antivir RegistryCleaner as well as the appropiate “Uninstallation Package”, both of which can be found at: http://www.avira.com/en/support/support_downloads.html
Okay, i will try this. Will remove Rising also and see what happens. Thanks.
I wanted to try and recreate this high cpu/memory usage. It happened again when I plugged in my USB key and started exploring and unzipping a file. I downloaded a Minidump tool that let me create a mini dump when avastsvc.exe was using alot of memory. Can I send this mini dump. Where and how do I do it?
Please, zip and upload the C:\Windows\Memory.dmp file to this anonymous ftp server: ftp://ftp.asw.cz/incoming
Please, go to folder \windows\minidump and send the newest (recent) .mdmp files for analysis. There is also C:\Windows\Memory.dmp file.
Better if you can compress (zip) them and add some information about the BSOD and the link for this thread. 
Thanks.
But I have one question. The tool I used was Mini-Dump tool v1 (http://bill.atwill.com/). It lets you create a minidump of a running process. I did not have a BSOD, just heavy cpu and memory usage, so I am wondering if the minidump is valid or not. I do not have a minidump folder or a Memory.dmp file.
Yes, it’s valid for freezes.
But, maybe, you can manually dump.
Manual dump: when the machine is in stalled state, hold down the rightmost CTRL key, and press the SCROLL LOCK key twice. This will cause a machine to ‘blue-screen’ and dump of memory will start.
In notebooks without the right most CTRL key, see http://forum.avast.com/index.php?topic=51847.msg440718#msg440718
To generate full dump instead of only kernel (or small dump), see http://www.msfn.org/board/creating-memory-dumps-t130005.html or http://forum.avast.com/index.php?topic=52652.msg446063#msg446063
Okay, thank you for the help. 