Turnpike/Norton conflict

My OS is Win2000. My ISP is Demon and I recently upgraded from Turnpike 6.02S to Turnpike 6.04S. At the time I was running Norton Internet Security 2004. The progress of an outgoing email is displayed in the Turnpike window up to complete, then a Norton window pops up and displays scanning progress.

Immediately after the upgrade, any message with a large attachment (I send Word documents frequently) causes the system to crash and restart during the Norton scanning process.

I went to Demon support as the problem followed their upgrade, and was finally told to go and ask Symantec why their program was causing the crash (everything is fine with Norton completely uninstalled). Symantec automatic support suggested upgrading to NIS 2005, which I did. Same result. There is no help in the Symantec knowledge base. I can't question them directly without paying them 28$, doubtless to be told that the problem is Turnpike.

Has anyone had a similar problem?

Thanks