Thanks for the replies! I fixed it and I post the fix (from Microsoft) here in case it helps anyone else:
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This information applies only to users running Windows Media Player 9 Series
Beta on Windows XP or Windows .NET Server together with a third party
firewall software
Microsoft has received reports of the Windows Media Player 9 Series Beta
crashing when attempting to stream from over the network when there is a
third party firewall software installed on the computer.
Problem:
On Windows XP and Windows .NET Server the Windows Media Player 9 Series Beta
calls into a new Winsock API for performance reasons. There are some
incompatibilities when using this API with existing third party firewall
software.
Microsoft is working to address these issues with the third party firewall
vendors.
Workaround:
The following steps are intended to serve as an interim workaround for the
Beta release of the Windows Media Player 9 Series.
NOTE: Following these steps are not supported and Microsoft is not
responsible for any problems that may occur as a result.
1) Quit the Media Player if it is running.
2) Copy the file c:\windows\system32\wmnetmgr.dll to the "c:\Program
Files\Windows Media Player" directory.
3) Rename the new copy of the file (in the "c:\Program Files\Windows
Media Player" directory) to wspwsp.dll.
4) Open a command window (click the "Start" button and select "Run"
then type CMD.EXE and hit enter).
5) Type in the following line into the command window and hit the enter
key:
regsvr32.exe "c:\Program Files\Windows Media Player\wspwsp.dll"
6) Run the Windows Media Player 9 Series beta and attempt to stream
content from over the network.
--
Eduardo Oliveira
Software Engineer
Digital Media Division
--
This posting is provided "AS IS" with no warranties, and confers no rights.
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C:\Wow