Hey Matt. Here is my setup. I set the recording to record 6 hours of Stern 7 days a week. I tell it to keep the last 5 shows and also have radio replay turned on. After about 30 days of doing this, my radio replays disappear, then my libarary erases and finally I get the "Can't play...." error.
If you google the error message, there was a LOOOOONG thread about it when the SL2 first came out. I am not sure if it's readable since it was on sirius backstage forums. I have also done all of the recovery, resets, upgrades available to me....I really hope the next one works.
In my opinion, its as if the stiletto has some software issue that consumes space or memory then kinda does a clean-up/crash fix. Once I reset/restore its fine for about 30 days, then it does it again.