Is the chain a Dura-Ace chain? If it is alot of people don't know that Dura-Ace chains have a front and back side u will notice on the chain it says Dura-Ace on one side and not the other. Side with Dura-Ace faces out very important my chain was doing the same as yours. The 7900 chainring has special pickups on the teeth to help it move up to big chain ring. The Chain is kinda rounded on one side if u look at.

Here is Tech Doc on it
http://techdocs.shimano.com/media/te...9830682232.pdf

Drive-train compatibility- there is only 3 chains that work on 7900 http://bike.shimano.com/publish/cont...ty%20Chart.pdf