Hey. I bought my XFX 6850 3 moths ago, and it's been working great. It made a little bit of noise, but it actually pretty quiet. Yesterday, I had to shut down my computer after it being unable to come out of sleep mode. When I turned it on today it was making a lot of unnatural, weird noise, and it i'm not sure if there s somehting wrong with the fan or anything along those lines.
You should make sure your fan is clean and dusted out first and foremost. Regularly. (I use canned air carefully and regularly)
I would also look in the AMD overdrive tab and uncheck
'Enable AMD overdrive' and 'Enable Manual Fan control'. There should not
be any issues with these default settings. If your fan is going South I'd look into a replacement card from from XFX.