Are you using a case or cover for your HTC Pro to protect it from drop, bump damage, etc?
I purchased one of the clear crystal cases from eBay.
Clear Case - HTC Touch Pro - Link fixed
I was afraid it would cause a problem with the sliding mechanism, but it actually fits perfectly. At first the slide was a little rough, but I found a clear piece of plastic on the backside of the phone that I did not even know was there.
I tried one of the black rubberized cases, but it was a little thick so I switched to the clear. I am thinking about losing the case and just spending the $7 a month for the protection plan.