I'm so sick of guys with theories based on the color of the sky,when I talk out of experience. I already have a HD 4850 which is properly cooled. Well the GPU is properly cooled, cause the VRM can't take an OC with those RAM Sinks.
Even guys with Watercooling have similar problems, cause that WC doesn't apply on VRM area, only the GPU gets cooled. Here's others with similar problems:
Bookmarks