First - Welcome to Mobilitysite.

Lots of good info and ppl here.
Second - If you can sync via a usb cable you probably have a bad cradle. This is not uncommon. Also, if your screen is scratched you may need to replace it. Here's a link describing how to take your AX apart. You'll have to decide if you can do it.
Instruction Video to Take Apart Your Axim X50 PDA