Well, I just did a complete reinstall of the OS and PS on a new hard drive. Installed the latest driver, and the exact same profile, and.....
everything works great now! I don't know what was wrong before, because it obviously wasn't the profile. I guess my unfamiliarity with OS X (just switched last month) caused me to break something in the early going.
Thanks for everyone's help. Sorry it turned out to be nothing too interesting!