I've got an XP machine running office 2007 which started having Outlook problems the other day. When you start a new message everything is fine until you click on the Insert Tab, then Attach File. You get the browse window and can click on the file to attach, but then Outlook freezes up. You can how ever drag an attachment onto the email with no problems at all, just when using the attach file command. I've run the (Office Diagnostics, and the office repair from the original install folder) both show no errors and complete fine.
All other programs seem to be running fine on this computer.