It's not quite the same thing but in case other people's searches lead them here too, I was having trouble getting Keynote (updated) and TextEdit to open. They would just hang without even getting to the initial screen. I fixed the problem by turning off iCloud for documents
Go to System Preferences > iCloud > uncheck "Documents & Data" from the sync list.
(Actuall I uninstalled Keynote, did the above, restarted and then reinstalled but I think I only needed ot do the above).
Anyway, both Keynote and TextEdit open fine now. Shame I can't use iCloud with them but I'll cope...
Hope that helps someone.
I had this problem too.
After trying lots of the suggested fixes, I managed to solve it by creating a new user account, logging into it, opened Pages (no problems there) and logging out of the new account again. I then logged back into my own account and iWork applications all launched no problems.
Hope this helps!