I got this error tonight while (tryinng) to record American Gladiators as well. All my OTA HD tuners where in use, so I used my newly installed XPS 420 ATI DCT w/Cable Card Tuners for American Gladiators. I just checked Medium and its recording fine OTA.
I've recorded a lot of programs in the last couple weeks with my DCT and haven't had this issue. I've never seen it on my four OTA tuners, using an HDHR, Hauppauge 1600, and Haupuuage 1800.
Since Vista obviously has DRM protection (for use with the DCT/OCUR) there is absolutely NO reason why it can't record the program and just protect it. After all, that is what every other DVR out there does. So why should be be punished because Microsoft follows the rules and no one else does? How truely Ironic really is this!?