Are you running WooGLE as a user or as an administrator? Your World of Goo installation is in restricted folder.

You should simply move your World of Goo into other localisation. If it's possible - outside C: drive. Then try to make and edit WoG levels.

Also NEVER edit your original WorldOfGoo installation.

Your level sounds cool. Can't wait to see it!

It is restricted, and the window that comes shows you are running Vista or 7. To fix this, simply right-click the shortcut to the editor. Click Properties on the context menu. Now, in the window that appears, click on the tab labeled "Compatibility". On the bottom of that page, tick the button that says "Run as administrator" and click save. Now, every time you run, it should come up with a security warning, but clicking "yes" every time should allow the program to work in full.

A better solution would be to copy WorldOfGoo to your desktop and use that. What Enchanter said would work, but any bug in WooGLE could corrupt your game.

Oh, and don't forget to patch.

As an administrator.
It worked! Thanks Enchanter, Albino Pokey, Pavke and Goosweek!