1. Check for an wandering battery clip...might have shorted out one of the batterys and drained it.
2.Using a battery tester with a meter or VOM meter check both the batterys - is one drained and one still like new? If so, probably bad quartz oscillator crystal draining the one(the one that is "-" side down?).
Most Hughes modules are difficult to replace the quartz crystal on :( , at least compared to some other brands.