Datasheet View Does Not Work in SharePoint 2010
This is a known and personally experienced issue (Tech Preview and Beta Builds as well) with Datasheet View not working in SharePoint if you have Office 2010×64 clients installed on your workstation.
Again this is one of the FAQ on the MSDN Forums and today I saw the solution posted on the thread, so comes this post for my reference and in case you experience this, then you know what is the solution to the issue.