Windows Vista AVGldx64.sys causing BSOD

I have Vista HP 64-bit SP1 and the free version of AVG.

It's never happened before today, but I've been treated to five BSODs in the last four hours courtesy of AVGldx64.sys, which was attempting to write to read-only memory.

I've temporarily disabled all AVG processes. What should I do?

 

After a reinstall of AVG, it still gave me a BSOD, so now I've switched to Avira.

I suspect AVG wasn't playing nicely with ZoneAlarm Extreme Security, since the AVG installer scolded me for having another security product already installed. I knew you weren't supposed to have more than one antivirus installed at a time, but the antivirus feature of ZA is and has been switched off.

I've used AVG and ZA together for years on three different machines, both XP and Vista, with nary a problem, so it must be this new version (the 64-bit beta).

In any case, Avira is working fine, so I'm satisfied.