- I've plugged this Mac Mini and adapter into three separate DVI monitors. No video from any of them.
- The HDMI port works, and shows beautiful 1080p on my TV.
- The Thunderbolt port works on those aforementioned DVI monitors using a Mini DisplayPort to DVI Adapter.
- I've tested the HDMI to DVI adapter alone (no Mac Mini involved) and it works great.
So the adapter works, the HDMI port works, the cable works, and the monitors work. Just not together, for some reason.
Other voodoo attempted (unsuccessfully):
- Ran a full Software Update. All updates have been downloaded and installed as of the time of this question.
- Put the Mac Mini to sleep, then woke it back up (using the Apple Remote).