Super geeky entry under the category 'PG Tips' here, but might be useful to someone...
I noticed my GPU was running really hot (over 90 degrees idle) so decided to open it up and see what was going on. Due to a not-very-clever design, dust was completely blocking the path of the air over the heatsink. If you have a similar graphics card, might be worth investigating!
Or if you can't be bothered going to such lengths, I would still advise downloading GPU temp or similar to check if it is overheating. (my temps dropped 15 degrees once i had removed the dust)
