Just lately have message (see attachment) that McAfee has found subject 'virus' in temp avast file at Windows/Temp/_avast4_/unp107660989.tmp ?
That is the folder where avast unpacks archive files that it is going to scan, hense the unp?
.tmp file name. The problem of having two active scanners is just that one can unpack a file for scanning and the other can detect the file on creation, this can cause a lock up.
So you should choose which AV to hav as resident and uninstall the other. You can choose an on-demand scanner or use on-line scanners as a secondary/back-up scanner. On-line Virus Scanners and other useful Links
Security-Ops.eu.tt