Try the quick and easy first...
Go to Finder "Go" menu hold the option key and choose Library. Then go to Preferences folder and trash these files:
Then, restart, or log out and in again.
(You will have to reset a few finder prefs the way you like them.)
Try starting up in Safe Mode (It will take more time to startup because it runs a directory check.)
If Finder functions correctly that way, go to System Preferences >> Accounts >> Login Items and remove them.
The log out and back in or restart.
Thanks MacJack, this solved my problem with new Mountain Lion upgrade. I was having major issues, but this cleared it right up. -
Actually, I spoke a bit too soon. It worked for a little bit but I'm back to having issues. Trying to copy 100 small JPGs from a folder to a flash drive, for example, leads it to get stuck in "Preparing to copy" mode, and never actually copies.
I migrated my user from a Snow Leopard system to a brand new Lion system and I have had this problem as well. I followed the "Safe Mode" tip, no joy. Then I restarted from the Restore Drive, and launched Disk Utility. It found problems. So I repaired permissions, verified the drive, then restarted.
I've now been using Lion for the better part of 5 hours straight without finder or file access problems.
It would seem that Lion doesn't like certain things when making the upgrade from Snow Leopard. Hope this helps.