With some help from Peter Gurevich, one of the IE 7 Performance PMs, I tracked down what caused IE 7 to basically lock up on my machine. Turns out it were the IE Developer Toolbar and IE DOM Explorer add-ons that were to blame. I disabled all but these two add-ons and saw no lockups any more.

I’m going to properly uninstall these add-ons so they’re completely gone and then I’ll be a happy IE 7 user!

Thank you Peter G for getting in touch!