I don't remember exactly how the time trax adapter is setup, but I have mine connected to an XM commander can that has external power. Whenever I disconnect my car battery I have to run the timetrax software to initialize the XM can. Once it finds the com port, it sends the serial initialization, and jumps to the last station tuned. I then close the timetrax software and everything works fine until the next time the XM Can loses power.
Give it a try, OBTW, you don't need to waste your money registering the timetrax software if you're only going to use it for the serial initialization of the XM can, the unregistered version will do it just fine.