Hi artie. I actually just tested it with a Mac mini we just got last week for use in the living room as an HTPC. No question about it... it's the monitor. It refused to boot also as long as the USB cable was plugged in. The moment I popped the USB cable out, it booted.
Unfortunately, I can't test a different cable... these are embedded inside the Cinema Display. So now I need to decide... new monitor, or spring for a new iMac (which I hoped to do in a year or so). Hmmmmm....
