I've been having this really weird problem with my R4. It seems like the filesystem likes to corrupt itself quite a few times on me. I first had this problem when I used LilouFTP and DSFTP. I tried FTP'ing into my DS to transfer and back up my save files. Ironically enough, this caused me to lose most of my saves. When I turn on my DS, 5 or so of my games (out of 18) have completely disappeared, and all my saves have completely disappeared too. Putting the card in my PC, I can see that most of the files are gone, but they still take up the alotted amount of space. Reformatting the card and starting from scratch didn't seem to help the first time, because my files randomly disappear again when I restart my DS. When this happened, I reformatted again, ran chkdsk, and re-downloaded the firmware and tried again. It worked perfect until today, when I tried to transfer a new game to it (Worms Open Warfare 2). Upon powering on the DS, 3 of my 18 games disappeared, with all their saves. Keep in mind that this is without using any homebrew applications, whatsoever. This is really, really frustrating. I really have no idea what's the cause of these problems and I'm hoping someone out there has had similar experiences or anyone has any idea what the the heck is going on. Using R4 1.11 firmware, and a Transcent 1GB MicroSD, if anyone is interested.