After finally getting around to uninstalling a release candidate of 2008 and installing 2008 Standard on one of the development machines, SSMS is consistently providing a :
An error occurred while executing batch. Error message is: Could not load type 'Microsoft.SqlServer.Types.SqlGeometry' from assembly 'Microsoft.SqlServer.Types, Version=, Culture=neutral, PublicKeyToken=89845dcd8080cc91'.

Error whenever a query is run in grid mode. The queries work perfectly in text mode.

What is the best way to fix this?