A CF-mod Rockbox iRiver isn't quite the same as something like an M10 or R09. The O/S is on the media, so be sure to:
- copy .rockbox to a safe place on your computer
- format the card via computer
- copy .rockbox back to the iRiver.
If you can't remember the last time you did that, then it's probably due. I wouldn't think you need to format it every show like most people do with an M10 or R09, just delete the old recordings and make new ones, and format occasionally, like every dozen shows or something. But I wouldn't be in the habit of constantly running with a near full card... if you have an 8gb card, don't get in the habit of having 6gb of old stuff on there and keep deleting and refilling the tail end of it... try to keep it fairly empty, or fragmentation will get you.