Taken from: Streaming errors in Windows Media Player
1. Close Windows Media Player. (To do this, on the File menu, click Exit.)
2. Click Start, and then click Run.
3. In the Run dialog box, type the following (exactly as shown):
%UserProfile%\Local Settings\Application Data\Microsoft\Windows Media
This step opens the following folder on your computer:
SystemDrive:\Documents and Settings\UserProfileName\Local Settings\Application Data\Microsoft\Windows Media
4. In this folder, rename the folder 10.0 to 10.0.bak. For more information about renaming folders, see To change the name of a file or folder.
5. Start the Player and try to stream the content again.