Further, Parallels must be version 7. If you were running anything less than that prior to upgrading to ML, you're out another $50 for a Parallels upgrade.
Hmmm - I have the E2P card and was looking to upgrade to ML early next week. FYI, I just went to the Sonnet site, and the E2P page lists it as "OSX Mountain Lion compatible", so I wold would assume they must have already done some testing.