Hopefully an easy one for the expertise around here:

I just got back to Texas from spending a year in California. My office machine used to be an ancient Dell P4 (2.4GHz) which I had connected to a once-expensive Apple Cinema HD display (23"), which has the funky ADC connector. I bought a Dr. Bott adapter, and it worked fine for years.

The monitor and computer were unplugged for the past year, collecting dust.

Now that I'm back, I bought a shiny new Mac mini (Core 2 Duo) and hooked it all up again. Initially, the vertical sync on the screen was miserable (shaky/flashy/annoying). The screen was effectively unwatchable. I spent a fair amount of time fiddling with the cables to no particular effect. After an hour or so, things mostly straightened out all by themselves. Now, the screen is mostly stable, but occasionally glitches.

Could this be related in some weird fashion to the adapter or screen warming up? Could one of the cables be bent up and damaged? Any other thoughts on what might be causing the problem?