Version numbers between the handheld and the desktop don't mean anything. As long as you have the Palm Desktop version that came with the T5, you should be able to HotSync--so something is obviously amiss. Does anything happen at all when you try to HotSync? (Does the computer give any indication that it's communicating with the T5 and does the T5 do anything, or do they just sit there like you never pressed the button?)