Boot from your recovery partition by holding down the key combination command-R at startup. Release the keys when you see a gray screen with a spinning dial.
When the recovery desktop appears, select Utilities ▹ Terminal from the menu bar.
In the Terminal window, enter “resetpassword” (without the quotes) and press return. A Reset Password window opens.
Select your boot volume if not already selected.
Select your username from the menu labeled Select the user account if not already selected.
Under Reset Home Directory Permissions and ACLs, click the Reset button.
Select ▹ Restart from the menu bar.
Launch the Terminal application by entering the first few letters of its name into a Spotlight search. Drag or copy -- do not type -- the following line into the window, then press return:
chmod -R -N ~
If you get an error message about permissions, enter this:
You'll be prompted for your login password, which won't be displayed when you type it. You may get a one-time warning not to screw up.
Then repeat the steps in my last message.
Your answer was useful again after I had a kernel panic, and then PowerPoint refused to save files, and Word kept crashing trying to open files due to permissions issues. One tip for people who don't run as admin is that the user running the commands has to be a sudoer. Also, there's one chmod that always fails to clear for me, but it doesn't seem to prevent everything else from working again:
chmod: Failed to clear ACL on file ubiquity.socket: Invalid argument