First of all ensure that you have at least webOS 3.0.2 installed.
Otherwise auto discover will not work!

Most of the time when you get an UPnP-Error something is wrong on server side.
Below is a list of known problems. Do you have another error? Please contact us.

Windows Media Player/Server

• UPnP Error 801: Access denied
  
  The device has no permission to connect to the server or the maximum number of clients/connections is reached.
  
  
  • Windows Media Player 11
    http://windows.microsoft.com/en-US/windows-xp/help/windows-media-player/11/share-media
    http://download.conceptronic.net/GRABNGO/FAQ/How_to_share_media_with_WMP11_EN.pdf
    (If you still have problems you may have to disable and enable the "Media Sharing" option or restart the computer)
    
    
  • Windows Media Player 12
    http://windows.microsoft.com/en-us/windows7/Getting-started-with-media-streaming
    http://windows.microsoft.com/en-US/windows7/Change-settings-for-streaming-media-in-Windows-Media-Player
    
    
  • Windows Home Server
    Use the "Windows Media Connect" Add-In
    http://www.wegotserved.com/2009/04/09/add-in-media-connect-configuration/
    http://download.chip.eu/en/Windows-Media-Connect-2.0_116694.html