I wanna buy MSI Ati R6850-PM2D1GD5/OC HD6850 1GB 256Bit GDDR5 but on the forum some claim that they had crash issues with 6850's: http://www.tomshardware.com/forum/304618-33-crash-issue-r6850
Is this really true? I'm not tech pro, so if you clarify that, I'll be glad.
Well, technically any hardware can crash your system. They're probably referring to game crashes when a GPU is worked hard and the game and/or system crashes. This is most likely attributed to a driver issue, but some cards have overheating issues or they just don't perform well because of manufacturing flaws.
Some folks will tell you that Ati/AMD has the worst drivers. I can tell you I've experienced crashes with any number of drivers, and I've seen where a WHQL certified driver has caused widespread issues with ALL the cards for that driver (nVidia and Ati).
If there are too many claims of crashes, then its probably a product to stay away from. Most cards will have a certain percentage of reported game crashes, but for the most part you shouldn't have too many problems as long as you keep you drivers updated.