2.6 Kernel and crashes on mouse click

I'm running Mepis 3.3, and when I launch it with the 2.6 kernel, I get quite frequent, random (I can repeat the same task, and yet not get the same results), and immediate computer system power-offs, with all of them happening immediadetly upon mouse clicks. When I run via the 2.4 kernel, this never happens. This has spanned across 2 motherboards of different make, but both using the Athlon XP processor. Has anyone else ever experienced this? It's as if the occasional random mouse click literally hits the power off button on my computer. I've had to abandon the 2.6 kernel due to this frustration. Is there a cure?