Yes! Problem solved!!
When copying I noticed an alias-script I wrote that was in ~/bin. I called it "find" and all it did was execute find and use grep to filter the permission denied messages.
Code:
find $1 2>&1 | grep -v "Toegang"
(In dutch you'll get "Toegang geweigerd")
After renaming this file everything worked like a charm and I'm happy again. I feel a bit stupid right now, but it's good to have the solution.
Thanks for your time and sorry for being this stupid