I have been playing much with 2010 (client and server) lately so it brought me a new problem with 2007!
If you have the Office 2010 CTP client installed and you try to run the SharePoint 2007 Wizard, it will fail quickly on step 2 with the error "One or more types failed to load”. Unfortunately, the only fix is to remove the Office 2010 client.
You can keep Project, Visio, and SharePoint Designer 2010 (which are different installs). You can reinstall the client after – until you need to re-run the wizard.