Problem with MP3s

[KMC61]

Just got my Bionic. Downloaded some tunes from my Amazon Cloud Player. They played fine in WinAmp. Then, I copied over my other mp3s from my other phone into a folder called Music. Now they play fine in WinAmp, but I cannot play the ones I downloaded from Amazon. I then tried to copy the files from the Amazon folder on my phone into the Music file, but the player says it will not recognize that kind of file (these are mp3 files, just like my others). I tried copying my mp3s from my Music file into the Amazon file....can't play those, either. Also tried to listen through the standard music player...no dice. I can listen to the ones I put on through either player, and I can listen to what still resides in my Amazon Cloud through its player, but cannot listen to both sets of tunes...