OK, regarding the crash, please try the following:
1. Schedule the boot-time scan of the area you want, but don't restart yet
2. Make sure you have the current virus database, which is 10101300 at the moment.
3. Download the file
http://public.avast.com/~glucksmann/aswboot.zip4. Go to avast! settings / Troubleshooting and disable avast! self-defense
5. Go to Control Panel / Administrative Tools / Services and stop the "avast! Antivirus" service, together with its dependencies. If you have avast! Internet Security, stop also the "avast! Firewall" service
6. Supposing you installed avast! into the default folder, go to C:\Program Files\ALWIL Software\Avast5\defs\10101300 (i.e. into the subfolder defs\10101300 of avast! installation folder) and extract the content of the ZIP file (downloaded in point 3) there - overwriting the two files that are already there
7. Reboot the computer - the boot-time scan should start
8. Simulate the problem and boot to Windows
9. Post the content of the file log\aswBoot.log again. For completeness, attach also the file report\aswBoot.txt.
Hopefully the log will narrow down the area where the problem occurred.
Thanks.