I didn't expect it to since it apparently doesn't work in w2k and the numbers of files that would be in the Persistent cache aren't going to be massive.
You need to get your head around the fact that avast doesn't initiate a scan it is a resident on-access scanner and is responding to activity, touching the files (executing them or opening them with write permission, etc.) that it is why scanning the files.
Turning off the file system shield not a kludgy solution it would be crazy as that is the very time when the file system shield is needed.
I would suggest that you try a clean install of avast 7.0.1426:
- Download the latest version of avast, 7.0.1426 http://files.avast.com/iavs5x/avast_free_antivirus_setup.exe
and save it to your HDD, somewhere you can find it again (if you didn't save your last download). Use that when you reinstall.
- Download the avast! Uninstall Utility, aswClear.exe find it here
and save it to your HDD (it has uninstall tools for 5.x, 6.0.x and 7.0.x).
- 1. Now uninstall avast! (using add remove programs, if you can't do that start from the next step), reboot.
- 2. run the avast! Uninstall Utility from safe mode, first for 6.x if previously installed and then for 7.0, once complete reboot into normal mode.
- 3. install the latest version, reboot.