XM protects their satellite broadcast from unauthorized use by having
the XM receiver carry an authentication code. I'm not sure how the
whole process works, but when you get a new XM receiver, you call
XMRadio, provide your radio serial number, and they respond by
broadcasting a code for a couple of hours that "enables" your radio to
decode the satellite signal that you've paid for. What's apparently
happening with a number of users is that the code stored in the
receiver is being lost, particularly when it hasn't been used for a
while, as in airplanes. The CV system then displays a screen message
that receiver activation is needed. You then have to re-dial XMradio
and have them re-send the activation signal. It isn't a big deal, but
if you just got to the airport and planned to launch into LIFR with all
your inflight wx data, you will either need to wait for re-activation
or launch without it. In theory, once you make the call, you can fly
and let the system update in the air, but these things are supposed to
reduce workload, not increase it.

CV has a new software release that assists in retention of the
activation code, but I recently defeated that by turning off my system
components in the wrong order. I'm good at this... :-(