Word 2007 on Vista problem which lead to Word freezing up after a document was opened.  At first we thought it was a bug in 2007 so as normal procedure we updated the office patches from the office update website: http://office.microsoft.com/officeupdate/ .  Failing this we moved onto the next troubleshooting step. My suspicions were that a word add-in had been corrupted or was preventing word from opening properly.  The fix is for this ended up being a simple proccess, it required a couple registry edits.  (remember to backup your registry before making any changes)

Open up Registry Editor: Start –> run –> regedt32 (or regedit)

CURRENT_USER/Software/Microsoft/Office/Word
Rename Addins -> oldAddins

After this step restart word, if it works you are done but if not go to the next step:

CURRENT_USER/Software/Microsoft/Office/12.0/Word
Rename Data -> oldData
Rename Options -> oldOptions

Article written by MyComputerAid.com