driscoll2

I bought my 99' TL used and just after the "20 second - 20 step" warrentee had expired, I started noticing that after my NAV-GIRL spoke, which would mute the stock Bose audio system, sometimes one rear speaker would remain silent, sometimes the speaker would come back on its own after a few more NAV announcements. Now it has gone away and hasn't come back. Fronts and the rear-deck sub work fine.
Any advice of a stratigy to diagnose this? Happen to anyone else?

Thanks in advance....