Problems with Windows Media Player 11 on Win XP Pro

Since having installed (reluctantly)WMP 11, I having all sorts of problems listening to anything but CDs. Internet radio, on line baught mp3 files, everything. I keep getting the C00D11B1 error message. And yet, when using Windows Media Player 6 or RealPlayer or any other player I have no problems. I can’t even uninstall the damn thing. What’s going on?