I use an application called Quicksilver. Some people call it a launcher, but it's much more than that. In fact, it does so much and is so useful that it's hard to describe. The Quicksilver site describes it as a "unified, extensible interface for working with applications, contacts, music, and other data." If you're interested, here's a roundup of Quicksilver tutorials and screencasts.
Here's how Quicksilver plays into this little drama. Quicksilver lets you set up triggers--keystrokes or mouse gestures--that control applications. I'd set up a trigger that used Apple-Option-Control-. to play iTunes (and Apple-Option-Control-/ to pause it). In OS X's Universal Access, it uses Apple-Option-Control-. to increase screen contrast. Apparently it captures the keystroke in addition to Quicksilver and I was doing it to myself. Any single increase wasn't enough to notice, but over a few days it built up until my screen was unreadable.
I apologize for unfairly maligning HP and Adobe. I wish there was some way to just turn all the Universal Access keystrokes off, but I can't see an easy way to do that. There's probably an XML file somewhere you can edit to disable them, but a cursory google didn't reveal them to me. So, I just changed my trigger.
Here's a story of another Mac user who had "screen problems" that turned out to be a barely engaged zoom in Universal Access. Ugh.