Does anyone else have this problem? I hit the sleep button, and when I slide it into the holster, the screen turns on. I am sure that I am not touching the power/sleep key, or any other buttons (which should be disabled). I have a leather holster with magnetized "clip". Any ideas how to prevent this unwanted screen "wake up"?

The magnetic holster is the culprit. I had the same thing going on. I would even lock my phone and when I would take it out of the holster it would be unlocked. I have the sliding keyboard sounds turned on and whenever I got my phone near the holster it would make the sounds as if I quickly opened and then closed the keyboard. This was unlocking the phone so I went with a snap closure holster and haven't had any problems since. I found a T-Mobile case that fits the touch pro 2 just fine.

The keyboard slide sensor is a magnetic sensor, likely a hall sensor. The magnet in your holster is triggering it.

I have a similar holster (Verizon stock holster) and make sure that I put the phone into the holster with the screen facing away from the magnet. I haven't had any issues. BTW, this is the same issue I had with my old Samsung i760.