i have xfx fx5900xt, but it's already broken, seems to be bad memory problem (artifacting on boot). It's starting to show signs of bad memory exactly a year from the date of purchase, so no rma. overclocking is done for testing purpose only, and i only do it maybe 10 times for 3dmark testing, since i don't think the performace difference by overclocking is tangible (at least to me). I have a 5 inch fan blowing some air to the card from the beginning since first i bought it, since it gets pretty hot.. , but that doesn't seem to help anyway...
regards,
gryfon