Having two resident anti-virus programs on the same system is not advised, it doesn't give you twice the protection, just twice the potential for conflict as you are finding out. You can use a non resident scanner as a back-up scanner or use on-line AV scanners for a second opinion if required.
avast has to extract files in archives in order to be able to scan them (the _avast4_folder and the unp?
?? (unpacked file) is where they are unpacked. The act of unpacking/extraction is being picked up by the second AV.