Log : http://nopaste.gamedev.pl/?&id=7268

IDLE 82C , FAN SPEED 85%
ONLOAD 100C , FAN SPEED 100% (black screen where bold text, the log last log input is after black screen, i think)
Code:
IDLE
        Date        , GPU Core Clock [MHz] , GPU Memory Clock [MHz] , GPU Temperature [C] , Fan Speed [%] , GPU Load [%] , Fan Speed [RPM] , GPU Temp.(DISPIO) [C] , GPU Temp.(MEMIO) [C] , GPU Temp.(SHADERCORE) [C] ,
2010-05-19 20:47:01 ,              625.0   ,               1003.1   ,               82.0   ,          85   ,          0   ,             -   ,                 82.0   ,                89.0   ,                     83.5   ,

ON LOAD
2010-05-19 20:44:05 ,              625.0   ,               1003.1   ,              100.0   ,         100   ,         99   ,             -   ,                100.0   ,               106.5   ,                    103.5   ,
2010-05-19 20:44:06 ,              200.0   ,               6393.8   ,               -1.0   ,         100   ,        100   ,             0   ,              32767.5   ,             32767.5   ,                  32767.5   ,
Ati Radeon HD4850 1GB with bundled cooler
Intel Quad Core 2.33ghz with bundled cooler / the chassi has a plastic cover enveloping the cpu with an outlet on the side.
Midi Tower Chassi with bundled cooler one inlet
2x2GB DDR2 Ram
Asus P5KPL-AM/PS Motherboard

Everything running with stock settings and latest updates, for example AUTO settings in bios for timings, or whatever
No overclocking done


When my temp reaches 100C I get a black screen (no signal on screen and I have to unplug power to restart computer). When playing games I can occasional still hear sounds though I get a black screen

So the question : is it a heating problem, I though GPU's should handle more heat?
And any tips on how to solve the issue, can take some photographs on my case if needed as i'm not sure what coolers fit and how the airflow should go