If errors are encountered compiling, Toad does not highlight the problem code or display what the error is. All it does is state, in the Script Output tab, that it "compiled but with compilation errors".
Instead of using Execute as Script button. Select Editor | Execute Statement (F9) or select Debug | Run instead. This will highlight the compilation error and give error message.
Note: Debug can only be used if license key has the Debugging option on it.
Waiting for fix in a future release of Toad for Oracle.