First of all I know this thread is a little stale but here goes. The problem could be just a loose connect with the cabling between the boards in your phone. If you've got the guts you could strip your phone down and re-seat the connectors. There are really only a few but it sounds like a digitizer problem or a keyboard problem to me. Either way, if you have a good pair of eyes and steady fingers then go over to Youtube and look for a video about bold 9900 disassemble or something like that and if you feel comfortable with doing the job then just buy a Torx T5 screwdriver from Radio Shack and go for it. The great thing is that since it's not your own personal phone you've got far less to loose if something goes wrong than most of us
PS, I don't suppose you've spilled water or food on it or had it in the rain or dropped it fairly hard at any point recently? If so then there could be bigger problems.