Kenwood DPX-510 not seeing Music Files

I have my Kenwood DPX-510 installed and going. What I can not get to work in my USB. I am using a SANDISK Cruzer 1GB flash drive. I am running Windows Vista and most of the files are WMA and I have even done MP3 from when Media player did the rip to MP3. I am just getting an error that states "No Music" and I am using the USB cable that comes with the head unit. I am thinking I am missing just very simple that is causing this issue but I am not sure. I just did a CD and that did not work either. I am not sure what is causing this.

***edit****

I did a CD in Roxio 7 for in a Mp3 and that did work. So now my problem is just getting get the USB to work. Thanks for any help.