Avast 6.x free locks up after pressing schedule now for preboot scan in vista

Avast Free Antivirus / Premium Security
1

Once again with the latest version of avast free 6.x (same thing happened in 5.x) after removing viruses from the computer in safe mode, I restart into normal win (only vista 32 or 64bit), install avast, enter the registration key, let it update the virus defs, then schedule a boot time scan (uncheck unpack archive files, choose move to chest, select only the system drive to be scanned, click ok on the settings) then hit the schedule now button and avast UI freezes.

I try to force a shutdown via command line: shutdown -r -t 1 and that never executes or I sometimes never even get to open the command line window after avast locks up. Must hold the power button to shut the pc off. It will then proceed to boot into windows but then start the preboot scan. I usually escape out of the scan and get into windows. If I try to hit the schedule now button again, it will usually lock up again. I think once the computer is properly restarted, it will allow me to do the preboot correctly without freezing.

How I normally fix an infected pc:

boot to safe mode
Install ccleaner, dfraggler, malwarebytes in that order
run msconfig, remove possible or not needed entries in startup
run windows firewall and reset it to defaults
reset winsock and proxy settings
reset internet explorer settings
run ccleaner and let it clear out internet cache, cookies, temp files etc. also use its registry scan and fix those issues it finds.
run combofix and let it delete the infected stuff
run malwarebytes and delete the rest of the bad stuff.
reboot into normal mode
run “powercfg -h off” to turn off hibernation
install avast and enter home user license.
and try to do preboot and that’s where i end up with freeze ups.

Doing this procedure in any version of win xp or win 7 works fine with no lockups.

Most of the infections tend to be rogue viruses, the ones that pretend they are an antivirus program but want you to pay money to get rid of what they find.

Any help?

2

Scheduling the boot-time scan doesn’t really do anything else than write a key into the registry… And if you have to power the machine down, it’s not just GUI freezing, it sounds like a lock somewhere in a driver.

Was there any other security tools installed - some behavior blocker that may monitor writing into auto-run registry keys, for example?
Or, though it would be very strange… would it help (i.e. prevent the freeze) if you stopped avast! Behavior Shield, before clicking the “schedule” button?

Well, I’d say the only way to tell more about that freeze would be to have a full memory dump, taken at the moment the system is frozen.

3

After using ccleaner I also try to uninstall unwanted programs or known spyware / junkware / other antivirus programs (norton, mcaffee, etc.). Obviously windows won’t allow me to remove all those programs while still in safe mode; so when I get back to normal I then uninstall what I don’t want. Does avast perform some kind of memory scan right after it gets installed? I tried a test yesterday, installed avast, let it update, reboot, setup boot time settings, hit the schedule now button, and it did freeze for about 5 seconds, but then I could reboot and all was well.

I’ll have to try and disable shield(s) before scheduling the next time I get a chance. Will let you know. Just odd it only happens in vista (32/64/any or no service pack) and not xp/7.