I had some problems including the Media Center guide issue, so yesterday I did a clean install of Vista on my 5-day-old Dell.

The problem I have is "Error 21" trying to update the guide. The full error message from Media Center is:
The Guide could not be downloaded for the following reason: Guide server error (Code: 21).

After the reinstall, it could retrieve the guide. So I started installing other software (Office, Adobe, etc). After each install, I would test the guide retrieval and it worked.

Today, it stopped working. No changes. I tried system restore - still would not work. I did a system restore all the way back to the clean install, and it would not work.

Searching the internet, I tried these potential fixes:
1. Delete the programdata\microsoft\eHome folder.
2. Rename programdata\microsoft\crypto\rsa\MachineKeys folder and create an empty one.

Neither worked.

The trace from programdata\microsoft\ehome\EPG\tracehelper which seems to indicate that the file is downloaded ok, but cannot be decrypted/expanded.  The error in the trace file is:  Data decompression processing error. Couldn't decompress and secure files

Any ideas? Dell support is of course no help.

I have the same problem.

See http://www.pcanswers.co.uk/node/5401#comment-11012

Have you found a solution yet?