try this:
enable avast boot time scan, see :
http://www.digitalred.com/avast-boot-time.php (if found anything, better to move it to chest)
and if asked to restart,
do not restart until you have done this too:
this will clear the page file on shutdown of the system
Here are the steps to configure this setting:
* Click Start
* Click Control Panel
* Click Administrative Tools
* Click Local Security Policy
* Click the "+" next to Local Policies
* Click Security Options
* Doubleclick "Shutdown: Clear Virtual Memory Pagefile"
* Select the "Enabled" radio button
* Click OK
come back and report.
nmb