Rarely, it happened a few times, my system started-up without avast ball in the system tray (and preventing thus AVAST from being loaded since the VPS weren’t updated as usual). I have to reboot to restore my system to normal. I have vista sp2 and Intel 2 core. How strange? Am I infected? ???
Am I infected?
I don’t see that you’re running x64… You could try a boot-time scan.
Or run a malware-bytes scan.
Usually this means that there were remnants of another A/V software, or a corrupt avast installation. A repair of avast may help.
You’re an avast Evangelist though, you’ve probably tried all of that…
Sometimes it could be a firewall interaction.
Sometimes it could be a Spybot (TeaTimer) one.
But you know, the icon is not the protection. When the icon disappears, is ashServ.exe running in background?
AVASTHOMEv.4.8.1275 <== should be v4.8.1335
COMODO 3 PERS. FW <== read about Comodo:
http://forum.avast.com/index.php?topic=46737.0
WOT <== too user driven and not subjective enough
SITEADVIS <== hopelesly outdated and still rates sites that contain known malware as Green
I would get Malwarebytes Anti-Malware (MBAM) instead of Spyware Terminator.
Just want to add I experienced yesterday the same problem with the Comodo FW icon in the system tray while AVAST was normally on. I went on the Security Center and it just tells me both my AV and FW are ON while their icon aren’t in my system tray. Anyway, when that happens I reboot for security. May be I use too much of Advanced System Care Personal by Iorbit, they do weird things to your registry and you get those kinds of surprises! 
Hi gdiloren
Well! … This Is Odd! ???
Coz…
Last week I started up my laptop and my Firewall failed to start up with it - PC Tools Firewall Plus - [b]
Then Yesterday…
I started up my laptop and my - Avast ( a ) was missing :o
Now this is the very first time I’ve had the missing ( a ) 
But then again that could simply be coz I haven’t been using Avast for as long as you have.
And I guess there are always times when computers decide to misbehave - Have a Blip! :
Note!
On the rare occasion when I’ve had missing security programs on computer start up in the past…
There has always been one of those horrid invisible Windows Updates a few days later.
I’m Trying To Think What It’s Called :-
Remember Now! … Windows Update Agent
But I haven’t found any evidence of one of those updates yet.
And Normally…
The same symptoms of security programs not starting up … Would happen on both my - Laptop & Desktop
But This Time… My Desktop Hasn’t Had Any Missing… [b] or ( a ) … So Don’t Know! :-\
I’ve ran a Thorough Scan with Avast.
But I might run a Scan with SAS too … Just To Be Sure!
Iobit do weird things to your registry ;D ;D
It’s been 4 days now, I rebooted and turned ON/OFF my PC several times and the weird phenomena didn’t happen again. I’m still a bit scared and puzzled about what did really happen but remembered it was also after the latest Windows update for Microsoft Silverlight & compatibility upgrade with IE 8. No leaks or loss of information apparently, thank God!!! 
well, as what I’ve seen last 3-4 years and working with very different computers (high end and very slow computers) one of the must popular problems for missing icons in taskbar is “launching many programs in same time” what usually happen in windows startup, because in that time many many services and also some startup programs launch in same moment. I’ve seen it happen in that moment and after a few second freezing (even 1-2 seconds) of taskbar so:
Wait a few seconds before enter username and password to login into windows in startup, by waiting before login you allow windows services to run before you login.
–in you have missed icons in taskbar, Log-off (not turn off/shutdown) windows and login after 4-5 seconds.
–disable those programs you don’t need from startup
–(for advanced users) change those windows services you don’t need from Automatic to Manual
–if you have a heavy program on your startup, disable it from automatic startup and create a shortcut of it to run it manually after windows boot time.