Error message when adding a new column:

Culture ID 1164 (0x048C) is not a supported culture.
Parameter name: culture

The file "Microsoft.SharePoint.ApplicationPages.dll" has not been updated in the app_bin folders for each virtual server.

1. Stop the IIS service.
2. Copy the file from 12Hive\Config\Bin to all app_bin which have SP installed
3. The version of the file "Microsoft.SharePoint.ApplicationPages.dll" should be "12.0.6548.5000"
4. Start the IIS service again.

Downgrade of Enterprise to Standard editon for Sharepoint 2010

Downgraded a SQL cluster from Enterprise to Standard edition. Removed the cluster nodes first, followed parts of this guide to downgrade the edition and then configured the cluster again (most time was needed for the cluster configuration).

If you don´t restore the master database, you need to run "GRANT VIEW SERVER STATE TO [MyDomain\FarmAccount]" to avoid flooding of "Event 5586" with error message "
The user does not have permission to perform this action."

One thing that is not to obvioulsy is that the "Property Store" and "Web Analytics Service Reporting" database uses Enterprise functionality and can not be attached to a Standard edition.
You need to recreate the Service Applications for the Search Service and Web Analytics. So plan for it beforehand.

The Search Service can not be deleted i the UI, check this how to use stsadm to delete it. You also need to delete the Search DBs in the same way or else the Event viewer will be filled with connection errors for the orphan databases.