Muvo C100 External Card Challenges

So I've been ripping music for my one gig SD card and, now that it's all set and ready to transfer, I'm having a hell of time - the darnedest time - trying to get the music to the one gig card. I've tried transferring via card reader and via direct connect (Muvo to computer, SD card installed in Muvo). Nothing's worked thus far. I keep getting the error "The disk is full." even though the one gig card has only 256 megs of music on it.

Only once did I manage to load 556 megs on the one gig card, only to open the card in the card reader and find more than half the files corrupted. The song titles were mismash with all kinds of estoric characters, like the card was cussing me out! LOL Clicking on a song yielded me nada. They wouldn't open. I went back to the computer to determine if the songs were corrupted to begin with and they're not. They're correctly titled and played with no problem.

I borrowed Guapo's 512 meg SD card and successfully transferred music filling the 512 megs. However, once the 512 meg card's installed in the Muvo, the Muvo sees only the resident 256 megs!! Bloody hell, I'm getting mad as hell. This )@$*&# MP3 player's not beating me. Oh, any suggestions???