>>>But what I'm curious about is why Avast interrupted the
>>>Superantispyware scan.
>>>Why didn't Avast find this trojan on any of many previous scans?
>>
>>Anti-virus scanners only work when they actually have the opportunity
>>to scan files. Since SAS was doing a full scan it opened the
>>"A00479214.exe" file for scanning and Avast then scanned the file as
>>part of the "on access" scanning function. The moral of the story is
>>that in order to be fully covered by any anti-malware program, you
>>need to perform full scans on a regular basis and not rely on
>>on-access scanning to catch the malware.
>
>
> OK, but I have done (do) full scans w/Avast on regular basis and it
> never caught this file before. Why now?

One possible explanation is that changes/updates in the Avast detection
signatures made it possible to detect the problem. Another possibility is
it's a false positive. You may want to scan just that file with another AV
program to see if the problem is confirmed.