I think I figured out why Jamlab doesn't work for me.
The drivers that are supposed to ensure 32-bit Vista compatibility aren't compatible with 32-bit Vista.
Which, yes, they're beta drivers, but you'd think that basic functionality wouldn't be spotty.
The device shows up fine in the Device Manager, but it won't start. The installed driver still shows up as the default (dated 2006) even after installing the update. Manually uninstalling the old driver and installing the most recent one has no effect. I believe the old driver may be installed by the device itself.
So I'm back to where I started.
I'm pretty sure I won't be buying any M-Audio stuff in the future. The support is just terrible. I can't even find any official forums.
On the other hand, I've gotten a look at Native Instruments Guitar Rig 2 and it looks mighty sweet. I have the fear, though, with computer audio, that things will not work or be glitchy or become obsolete. Understandably.
Plus it's a fuckload of money (370 bucks) to drop on noodling gear.