I'm was running WCE 2002 with SP2 and everything worked fine.  As soon as I updated to SP3 I get the following error message when I try to open Media Center:

ehshell.exe - Strong name validation failed

Strong name validation failed for the assembly 'C"\WINDOWS\ehome\ehshell.exe'.  The file may have been tampered with or it was partially signed but not fully signed with the correct private key.

My only option is to click OK.  Then the second window reads:

ehshell.exe - Common Language Runtime Debugging Services

Application has generated an exception that could not be handled.

Process id=0x97c (2428), Thread id=0x994 (2452).

Click OK to terminate the application.

Click CANCEL to debug the application.

I've searched the internet for a resolution and found nothing.  Replacing the file with the backup in C:\WINDOWS\System32\dllcache had no impact.  Any suggestions?

As documented in Windows XP SP3 Release Notes, Windows XP SP3 update Windows XP Media Center Edition to Windows Media Center 2004.

You are missing runtimes for Media Center 2004 is Microsoft .NET Framework 1.0.3705 and It's SP3

Download : Microsoft .NET Framework 1.0.3705 and It's SP3

that message migtht due to the improper working of .NET framework.....for MCE without rollup2 .net framwork 1.0.3705 is sufficient ..........

for rollup2  ver.1.1.4322 required ......install proper ver.of .net and try...

I've run into this error myself. The cause was ffdshow or something or other installed with KLite Mega. I've since did a minimal install of KLITE and no more errors. So it could be a codec. or not.