Working fine on *nix (Mostly Gentoo Linux, and OS X) boxes over here. Do you have another distro/OS or another FAT USB device to try, just to see if it's not your F13 setup doing some crazy stuff?
I seem to remember having devices remounting ro on the fly because of sw/hw failure a while back...
Do you see something relevant to that in dmesg/system logs?
Last edited by NiLuJe; 08-17-2010 at 10:29 PM.