I found this problem in a couple of other posts, but their solutions didn't work for me. Here's the deal: My phone is about a week old. I downloaded two ringtones that worked for three or four days. Now, neither of them work because I'm getting the error message in the subject line above. Also, before I knew about this problem, I downloaded two other ringtones that are nowhere to be found.
Restarting the phone didn't fix it. Removing and reinserting the SD card didn't fix it. Any ideas?