Since it's on 2 machines, I'm guessing that you did something, or transferred something from one machine, that is screwing things up.
Your post indicates that you generally work in a user account without admin privileges and that you have to login in as admin when you have the problem. If so, log in as admin and look at the user account that you normally use for restrictions. Depending on the OSX version it can be listed as parental controls or restrictions. With those restrictions you'll see things like burning cds/dvds. If that's the case, turn them off.
Another option is to go to hard drive/user/library/preferences and trash prefs for Finder. It's called com.apple.finder.plist. Then hit Command Option Esc on the keyboard to restart Finder. Best to do this with no other apps running.
I'm guessing that, since the problem is intermittent, that you have unintentionally introduced some other problem to the OS. Rather than pulling your hair out, it might be worth it to reinstall OSX using the Archive and Install option. It come up when you click the Options button on the first screen f the installer. Archive and Install keeps all your settings and stuff - so you don't lose anything. The see if the problem goes away.
Using OSX 10.3.9 & 10.4.11 on a G4, G5 & Intel Macbook
