Maybe this thread is similar to http://www.avast.com/forum/index.php?board=2;action=display;threadid=1486.
Although, your trouble seems to be related to the printer drivers…
What is the extension for the files at spool (try to print something and see the printer spool, generally at, C:\WINDOWS\system32\spool). Is avast! set to scan this particulary kind of file? Are you scanning all files?