I have had a couple of weird problems too but don't know if it is Pprune or Zone Alarm.
I have just upgraded (
) to ZA Extreme Security and when getting into Pprune find I keep losing my log in. Then when I drill down to open a thread I get the BSOD.
I suspect an interaction between Pprune and ZA. I have disabled Force Field for the moment and touchwood it seems to be more stable.