:bump:
I've been kind of busy and only recently found time to fully tackle this problem.
Sevoma: the error you referred to no longer occurs, thankfully, yet I did a dist-upgrade anyways.
I tried to find the refresh rates for this monitor (Apple Studio Display, 17" CRT, clear) but couldn't find a manual. Mac OS 9 and X both use a refresh rate of 99 hertz on my monitor, so I tried that. No luck.
I found a manual for a similar model, which used 60-85 vert. Still nothing.
I have a feeling it's a horiz problem, but I don't know...