AS5, no doubt.
Alot of the newer cpu's with the heatspreader over the core (P4 and A64), will "stick" to the HSF. However, this is not due to the paste being adhesive, but because the larger flat surface of the heatspreader creates a vacuum with the paste between the cpu and HSF. To remove the HSF, simply loosen the retention mechanism and give the HSF a very slight twist. This will break the vaccum and allow the HSF to be removed easily. Don't just pull on the HSF, since you can potentially pull the cpu right out of the socket.
Edit: Zepper's comments about WD40 seconded. WD40 just seems like it would smell bad, leave your proc greasy, plus, it's flamable. I personally use isopropyl alcohol. Cleans up Arctic Silver really well, and leaves the proc squeaky clean, dry, and oil free.