4870 problems

[Hallowed_Dragon]

Ok, this might sound extremely stupid, but the cooler of my 4870 seems to be blowing air instead of sucking air in and blowing it out of the case (dual slot cooler). The card overheats and I am forced to keep it well below its stock speed. The fan works at 100%.
Did this ever happen to any of you?

 

[cusideabelincoln]

Dust is probably clogging the inside of the cooler, blocking airflow.