Windows Media Player cannot open a .wpl file from Web page in Internet Explorer 7 on Windows Vista
On a Windows Vista computer, you click a hyperlink to a .wpl file. If the HTTP header returned from the server contains content-disposition with a file name that includes encoded characters (for example, testwpl_02%2B02%2B2009.wpl), then Windows Media Player may report the following error:
“Windows Media Player cannot find the file. If you are trying to play, burn, or sync an item that is in your library, the item might point to a file that has been moved, renamed, or deleted.”
For more information on this issue, including potential causes, workarounds, and resolutions, see: Microsoft KB Article KB969045.