Hi, I have been in touch with Ad-aware and was told:
During a scan, Ad-Aware will temporarily decompress files to scan their contents without activating the content, but in doing so, the file is noticed by the antivirus' resident scanner. Also, some antivirus applications include an option to quarantine infected files, and when Ad-Aware decompresses these quarantined files, the antivirus background scanner detects the virus moving outside the quarantine area.
So I don't think there is anything to worry about.
Thanks for your help.
Mike.