Strange behaviour with P4P800 + FX 5600 /w 44.03

I have recently put together a new machine based on:
ASUS P4P800 Deluxe mobo (latest BIOS 1008)
P4 2.8 Hyperthreading (800Mhz FSB)
ASUS V9560 Geforce FX 5600 (NVidia 44.03 drivers)
1 Gb RAM

Once in a while (every other day or so) the desktop "corrupts" and
"zooms" in on the top left corner of the screen. It's a bit hard to
explain, but imagine seeng the "my computer"-icon with inch-size
pixels on Y-axis and somewhat smaller on the X...
The odd thing is that everything seems to work. The mouse pointer
seems normal, and if I click on the position of the screen where the
"my computer" icon used to be, I can select it... If I check the
timing on the monitor everything seems normal 1600x120085Hz... I even
managed to bring up monitor settings in this "corrupt state", and when
I changed the refresh rate to 75, the whole screen came back to
normal... Has anyone got a clue? Has anyone seen similar behaviour?
Hardware issue? Driver issue? (Driver + hyperthreading, maybe?)

I have seen in this group that 44.03 is not a very stable release, so
I'm currently running 44.67 to see if it helps...

Regards!

//Thomas