Hey Dirk,
Sorry to hear you are having some problems, sounds like it just may be the connection from the trutrac to the computer (cable and/or serial adaptor). It is also possible that the driver file may have become corrupt.
Best bet is to email the TruGolf Tech Support first, then while you wait, try to test the cable, serial adaptor, and reinstall the driver and/or test on another computer.
Hope that helps,
Happy Golfing!
Cory