I "think" your situation is caused because VC connections do not allow for a mixture of different speeds; may actually run LACP under the covers, which does NOT allow for mixed speed with a LAG (yes VC forms an automatic LAG). If you connect the 40GE and disconnect all the 10GE does 40GE now come up - this would prove it. I would suspect that once 40GE is up, if you replug in the 10GE they will no longer come up.
This is my quess, but I think sounds reasonable. Good luck.