The fact you don't get an XM signal when
testing will make it pretty difficult to identify. After coming out of hibernation, and going into the XM
Radio settings, It "looks" as if I am getting no signal (i.e. it shows that I have XM enabled and the receiver ID is there, but the signal bar shows nothing even know I am in clear range of an XM signal.)
Since you are trying this w/out a signal, after returning from Hibernation, try clicking the "Enabled" check box in the Radio Settings. Mine it won't allow me to uncheck/recheck it... After clicking a few times it will kick me out of the program.
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