Magic Trackpad Pairing Procedure Document: Where?

My Magic Trackpad ran low on batteries, and after changing out the batteries, pairing is failing. I can't seem to find the documents describing how to Bluetooth-pair the Magic Trackpad with my Mac Pro. Anybody know where a description of the procedure can be found?

In particular,

• Bluetooth is "on" and "discoverable" in the Mac's Bluetooth System-Preferences panel, and the trackpad shows up in that panel.
  • Sometimes it shows up as "connected," but more often as "not connected." Not sure what to make of that. Connecting it often doesn't seem to be successful.
  • The trackpad also shows up as "Paired - Yes," and "Configured - Yes," even when it's "not connected." Perhaps that just means, correctly, that it was paired at one time in the past...
• I pop up the Trackpad System-Preferences panel.
• It initially says, "no trackpad found" and "searching."
• I hit the button on the side of the Magic Trackpad.
• The LED on the trackpad goes solid-on for a second or so, then blinks.
• It (after a few seconds delay) says "Found Apple Wireless Trackpad."
  • However, sometimes it doesn't find the Trackpad.
  • Sometimes, if I cycle power on the trackpad, it does find it.
• When it does find it, though, I hit "continue."
• It says "the pairing attempt was unsuccessful."

As far as I can tell, there are no other Bluetooth-enabled devices in the vicinity, potentially interfering.

Oh also, I'm wondering if the System Preferences panel, and SW for it in general, for it might have vanished somehow. The Preferences panel shows a picture of the Magic Trackpad, so it may know that there's supposed to be one "out there," but it doesn't show any of the controls for any of its cool, multi-touch features. Maybe it's not showing those controls just simply because it hasn't paired yet.

I remember I had somewhat similar difficulties setting it up the first time too, and I can't remember what the final solution was. It worked great for a long time after that, until now.