I finally tossed in the towel on Avantgo. Their pathetic lack of Mac support is one thing; there are workarounds for that. But they didn't even support Palm OS 5 (which the Zire runs on) until recently, and now that they do, you can only install it via Windows. So in a fit of insanity, I installed Virtual PC and tried to get it to talk to the Zire. No dice.
But that's ok, since I found a program called iSilo, which is way better. It does everything that Avantgo does, plus it reads ebooks and is really customizable. No restrictions on the number of sites you can access, either. It costs $19 US to register, but I think these cats deserve my money (much like the good people at Audio Hijack).So screw you, Avantgo. You aren't quite as useless as Telus, but you're close.