I would side with the rest of the group here in that it is probably faulty memory, improperly seated memory, dirty slots, or wrong memory speed.
The fact that the problem occurs with Norton installed is merely the fact that Norton scans the memory...my guess, or at least is trying to use certain portions of it.
Definitely try returning/replacing the modules to see if the problems go away.
Doug
dxd_2000@yahoo.com