Hi have you tried a system restore from the recovery console ? If not try that first
There appears to be a problem with a few Vista systems where windows updates breaks the system, sometimes removing Avast will clear it and sometimes not. I have not been able to find any specific circumstance which causes this
If the restore fails then using the fixlixt attached I will remove Avast, again this may not cure the problem
Download the attached fixlist.txt to the same location as FRST
Run FRST as before and press Fix
Try a reboot to normal windows