Similar to what this user sayssearch.php?author_id=5981&sr=posts
I have the same issue. Albeit HTC Rezound is not a 100% supported app, it seems when you map a hardware key (which is limited on the Rezound as it is), when you go to press a virtual key it will cause it to release the hardware key.
The odd part was that I did not have this issue before the latest update. Prior to this latest update I had sound issues which were resolved in this latest update but a regression on the hardware mapped keys and virtual keys. Also, another odd part, was that this issue DID exist previous to this update but only affected the keys on the bottom of the phone (like back, menu, etc) but did NOT affect the volume up/down (which is ironically enough the same keys I was using for aim in RE2 like the user mentioned above).