Intermittent Sirius Sigma operation

I've had my Prius since May 2nd. I'm liking the car more and more as I get used to sitting down low (I've been driving Ford Explorers since 1998).

I've been having a problem with my Sirius radio not being available when I start the car. Pressing AM/Sat doesn't do anything but stay in AM. Sometimes when I start up the Sat radio function appears, but it's totally blank (no station, no indication of lost signal). Under the second condition powering the car down sometimes results in the first failure condition. I can usually get the Sat radio back by powering the car up and down once or twice. Then everything is OK for a couple of days before it comes back.

The system is the one supplied free of charge with an inside Sigma antenna and a free 9 month subscription.

I'm thinking that it's some kind of problem in the Radio's aux input and it's not recognizing the Sirius radio.

Has anybody seen anything like this?

Sy Cohen