While upgrading to Exchange 2010 Service Pack 1 you may receive the following error during the readiness check:
Language packs are installed on this server and must be upgraded with the Exchange binaries. Please specify a language bundle with the upgrade operation.
Download the language pack from the Microsoft website instead of using the one on the DVD:
Run Exchange 2010 setup again. Click Upgrade all languages from the language bundle.
Set the path to the language bundle you downloaded from the Microsoft website.
Now when setup runs it will pass...