Upgrade Causes Slowdown or Freezes
Sometimes following an upgrade your computer may slow downs considerably and/or “freeze” when a program accesses the keychain. This is a known issue in the OS X keychain and has been reported to Apple for resolution. You can see this forum thread for details.
There is a simple work around, however. Effectively what is required is to delete a temporary file used by Mac OS X and force it to rebuild it, thereby fixing the problem. You can do this by using Finder to drag this file to the Trash:
/var/db/CodeEquivalenceDatabase
The /var/db Folder is hidden by default in Finder, so you need to use Cmd-Shift-G to open the “Go” window, and type /var/db into it. Once there, drag the CodeEquivalenceDatabase file to the Trash, and enter your administrator password if Finder requests it. Once deleted, reboot your Mac and the problem should be resolved.