It can't go back to HC with a factory reset if the ICS update actually completed. That would then be the only image on your ROM. If you just got the tablet though, there may have been a few HC updates that are prerequisites to ICS, meaning that you may not have hit Android 4.0.3 yet.
You can look at Settings-->About tablet to see the Android version. The most current HC is 3.2.1, and ICS is 4.0.3.
Odd problem though. It's good that you have warranty coverage.