License Problems

[MrsMustang]

Morning,

I have a Zen and Zen Vision M I am starting to have problems with the past two weeks playing back songs. I rip Original Cd's to my PC and also buy music from Napster and randomly on both players I am getting error messages to download the license from the PC. There sems to be no pattern on which songs are getting error's. I find it confusing that a CD I rip to a PC would do this. I have no idea where to even start to try to correct this because I am not familar with what actually transfers with a music file. I can tell you both players have the latest firmware updates. But I do think I am not using the latest Windows Media player, if that has anything to do with it? Any advice?

Thanks,
Mustang