Drupal content encoding error - Inhoudcoderingsfout in firefox 3

Dutch
Inhoudcoderingsfout
De pagina die u wilt bekijken kan niet worden weergegeven omdat deze gebruikmaakt van een ongeldige of niet-ondersteunde vorm van compressie.
Neem contact op met de website-eigenaars om ze te informeren over dit probleem.

English

Content Encoding Error
The page you are trying to view cannot be shown because it uses an invalid or unsupported form of compression.
Please contact the website owners to inform them of this problem.

This has nothing to do with the client side. It is due to a compression error on the server. The pages are send to browser gzipped and the browser cannot interperet the decompressed stream.

On drupal sites it is a page caching problem. If you have latest core you shouldnt experience the problem.
A quick fix is turning off page cache.

For more information :
http://drupal.org/node/282110