I have found that AS Spy Sweeper v.4.5 scan is conflicting with [Ashserv] during a AS scan. The “blue screen of errors” occur and hang on this file forcing a reboot of the system. 
Are you using Windows XP\Vista?
If so, please, go to folder \windows\minidump and send the newest (recent) .mdmp files for analysis.
Better if you can compress (zip) them and add some information about the BSOD and the link for this thread. 
Send an email to any of these addresses:
vlk (at) avast.com
rypacek (at) asw.cz
Or upload to the any of these anonymous ftp servers:
ftp://ftp.asw.cz/incoming
ftp://www2.asw.cz/incoming
win98se 
Hi, I want to add that the AV scan with Avast is ok. This is only when scanning with AS Spy Sweeper v.4.5.x that the crash occurs and that I have sent a report to Webroot about this problem. Also the online scan sheilds of both programs seem to work ok together. 
:)Today I had a scheduled scan with Spy Sweeper 4.5.x and the option to scan all files on local_C drive. Before the scan I took down Avast on-access scanners; the run was executed without incident. I will test this again later this week using the on-demand scan option and the limited files and folders option most likely to contain spyware to determine if this problem is in the clear, and post back the results.
I may try this with on-access scanners for Avast on if time allows. I do not think that there is a danger running this program with the Shields down since there is no download or access to any files other than the scan itself and I have already run Avast in all three(3) modes and with and without archives. So it is most likely safe to do this. 8)
The problem is probably a web or standard on-access shield in Avast that is complaining about the other vendors scan process. Spy Sweeper does scan each file thoroughly. >:(