pc freezing w/ new hd3870 card

i recently replaced a x1950xt card w/ a visiontek hd3870 card. since i replaced it, my computer freezes up when playing games usually after about 30 minutes of playing. i only play racing games so they are not super demanding. i'm getting over 100fps at all times w/ the settings i'm using, so i'm not over working the card, and the temps are never going over 70c.

i've tried installing various versions of ati's ccc, and am currently not using it at all, after removing it and using a registry cleaner to clean up after it. all i have now is the driver and rivatuner to control the fan, and it still does the same thing, although it does seem to take a little longer for it to happen now.

any ideas?

i'm using a progressive fan speed to temp setup:

fan speed/temp
40% @ 45-55
50% @ 56-60
60% @ 61-65
70% @ 66-70 <= while racing it tends to sit here, right at about 68-69 degrees
80% @ 71-75
90% @ 76-80
100%@ 81-100

yes it works great, but you cant use the setup that comes w/ rivatuner, you have to set it up a more complicated way for it to work w/ this card anyhow.

here is the link to the instructions showing how to set it up:

http://forums.overclockers.com.au/ [...] p?t=686008

ps is corsair hx520