I haven't used this substance before, but there are some thermal conductive
glues, such as the one noted in the link below.  This would be a permanent
bonding of your heatsink to your chip, but it may be the best option under
the circumstances, since you can no longer use the clip to clamp your
heatsink in place.

http://www.kdcomputers.com/exec/productProfile?id=10

You can follow a link on the above page to the manufacturer's website and
find some detailed directions on using this product.

John

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