With the new virus definitions - in addition to Avast deciding that skype is infected with Win32:Delf-MZG - Thunderbird (the Mozilla mail client, version 2.0.0.23) is running terribly slow, and a bit flakey. Every incoming or outgoing message takes several minutes for Avast to check.
You can say that again, I unplugged my internet access and stopped Avast and then cleaned out the emails and hope they fix it soon.