Hmmm, I have never encountered such a thing before, but let me see what I can do...
But I think any of these two methods should help :-
1.Right click on the world editor Icon
2.Go to properties
3.Go to the compability tab.
4. Tick the box saying run this program in compability mode.
5. In the field saying "run this program in compability mode for - " select windows 2000
6. Restart the Editor
--------------------------------------OR--------------------------------------------------
1.Open an antivirus software (download one if you don't have)
2.Run a scan on your Wc3 folder
3. If you find any threats, remove them.
4.Open the editor.
If this does not work then please message me, I may be able to help.