Can't assign keyboard shortcut to service

Solution 1:

One possible reason is that your user account has lost rights to change services preferences file (some buggy installers can cause that). Open Terminal and type

ls -la ~/Library/Preferences/pbs.plist

If you see that the owner is root, that is the problem:

-rw-------    1 root  wheel    1407 Jan 16 13:40 /Users/me/Library/Preferences/pbs.plist
                  ↑
                 incorrect!

In that case, you can fix the problem by typing this command (replace me with your user name; you will be asked for your password):

sudo chown me:staff ~/Library/Preferences/pbs.plist