Thanks f0dder & Tinjaw (f0dder mentioned the auto restart tip in his post too
) . It was probably a loose connection then - most likely to the gfx card. I thought of swapping the adapter ports coz Dxdiag (esp. directdraw test 2 - the block bouncing in 'normal' mode) was clearly more responsive for the non-DVI output, it started off a bit slow on the DVI port before picking up speed.
Though the PC didn't restart on its own during these freezes, I did have 'Automatically restart' enabled, it obviously makes sense to have that disabled. In my case the BSOD flickered for a split second before the display got garbled again - no restart though. I have been running with a paging file
Spoiler
read something on TweakGuides about Windows absolutely needing one, irrespective of mem size
but on another drive so it sucks to enable it on C: too, for the mem dump. I'll know what to do the next time something acts up tho.
PS: The freezes were sporadic but one particular OpenGL screensaver (Euphoria, from the ultramon people) jammed things up every single time. Just out of curiosity: We keep regular DirectX updates but what about OpenGL? How does one go about updating their libraries?