[warped79]

Not sure if this is any use to anyone (it's an old thread but I found it when I was searching this problem).

I upgraded from Pro Tools 10.0.0 to Pro Tools 10.2.3 and I had this problem.

This is what I did wrong:
1. When I un-installed my 10.0.0 pro tools installation I chose option 1 'Pro Tools Only'.

Then when I installed Pro Tools 10.2.3 I had the problem described above (I deleted all my pref's, DAE prefs, Databases, did the optimisationi and nothing worked.

To fix this I went back to control panel, and un-installed Pro Tools - this time I chose option 3 'Pro Tools, Avid HD Driver, Preferences, Databases and MIDI Device/Patch Settings'.

Re-booted my machine, ran the 10.2.3 installer, rebooted again and it launched straight up and works fine (so far).

Hope this is useful to someone out there
Daz