I have had the problem in my last car. Tried torquing the bolts a little, but it actually made it worse. What made me mad is the valve cover gasket was new from when I replaced the head gasket... Well, long story short you just have to make sure you clean the surface very good with mineral spirits, or something to clean off the oil.

Not too sure how to do it on the Crossfire although I assume it is a similar process. Basically you will need a manual to tell you the pattern of torquing the bolts and what value to torque them. I'd rather nag a dealer than to do it myself though, especially if you have a warranty...