Thanks for the help. I put 2 pieces of index card cut to the size of the sticker as shims, wrapped a little bit of scotch tape around it to hold them in place. It's definitely a more snug fit, but it didn't fix the problem. I guess he just sold me a bad card along with a DS I can't use now.
I purchased a DS Lite a couple weeks back with only a CycloDS card, had no games with it. I purchased a SanDisk 16gb micro sdhc card, formatted it with an SD card formatter and everything. I loaded up a backup game and for like a day everything worked. Then, the next time I turned it on, and...