How about this: Anyone with a capcitance meter? Arctic Silver's manufacturer says that AS should not be conductive, but that it might be slightly capacitive.
OP: Best bet would be to just head down to Radio Shack and buy a conductive pen. It dispenses this liquidy stuff that probably will look like Arctic Silver, but it is conductive. I've also heard that there's a liquid used to repair window defrosters in cars, so that might also do the trick. It used to be popular for closing the gaps between the bridges on the good old AMD Athlon, T-bird, T-bred, and Palomino processors to enable overclocking.