Avast Add-in for Outlook 2007 causing problems

Hey, figured this would be the best place to ask about this; on Outlook 2007, whenever it receives a new email, it freezes (not responding) for 20-30 seconds, then works fine until the next email (doesn’t happen when it syncs and there’s no new email). It didn’t do this in Outlook safemode, so I tried disabling all the add-ins (all default) one by one, until it was just Avast add-in left; still froze when receiving new emails. Once I disabled the Avast add-in, it receives email just fine, no hangs or anything. Also, this problem only started when my mail server switched to IMAP. Any ideas what could be causing my problem?

Windows Vista Enterprise (64bit)
Avast! Free 2014.9.0.2008
Outlook 2007 (12.0.4518.1014)

No suggestions? None at all?