Avast 5.1.864 (and lower) very slowly checks files packed PEtite 2.x-> Ian Luck, for example a known sound engine bass.dll and its other additions from site http://www.un4seen.com/, or this http://www.multiupload.com/3SUIFSXHDS please improve it.
That’s not fully correct - unpacking of the public versions of Petite is quite fast. Bass, however, it packed by a private version (since the author of bass is the author of Petite), which is not supported by the internal unpackers.
You can put the affected files into the list of scan exclusions.
Very bad :-X, but other antiviruses check bass.dll very quickly
Is it possible that some aren’t unpacking it at all.
Maybe, I do not know.
The only reason I mention it is that avast has one of the best range of supported unpackers. So there is a higher likelihood that it will be unpacking compressed files for scanning.