Walker,
The general rule with Avast is simple. You should not have 2 AVs running resident at the same time, especially AVs with email scanning such as AVG by Grisoft. Most of the other manual AVs are ok. I have used the on-line Av scanners as well but shy away from Panda.
Computer Associates, Symantec and Kaspersky worked ok and did not interfere or mind having Avast around.

To lessen the likelihood of conflict, with any other AV, shutting down the On-access protection moducles of Avast should be fine.
Technical suggested AnalogX Script Defender. This is a good choice. Also look into Script Sentry ( which I use with the Avast Home version).
Both are well suited to protect against malicious script execution.
I think you still can download it at
http://www.jasons-toolbox.comGood Luck
techie