If it was AS5 then the chip might be shorted.
Regardless I'd clean it anyways and hope.
Artic Silver 5 is NOT conductive but it is capacitive. There is a difference. This is right from the manufactures website:
Not Electrically Conductive:
Arctic Silver 5 was formulated to conduct heat, not electricity.
(While much safer than electrically conductive silver and copper greases, Arctic Silver 5 should be kept away from electrical traces, pins, and leads. While it is not electrically conductive, the compound is very slightly capacitive and could potentially cause problems if it bridges two close-proximity electrical paths.)