We have updated 4 of 7 systems, 2 of which have the same issue you are having. The system specs vary somewhat but they are all running Windows 7 with both CS5 and CS5.5 (we are testing before fully migrating).
2-Decklink HD Extreme 3D cards (1 is still running an old driver, the other running the new driver without audio).
5-Intensity Pro cards (2 running an old driver, 2 running the new driver perfectly fine, and 1 running the new driver without audio).
We tried to rollback the driver…but it actually didn’t solve the audio issue even though the audio had been working previously.