Netbeans 6.5 Bug when using Groovy

For a project I'm using Netbeans 6.5 and the GroovyScriptEngine out of the Groovy-Package directly. Therefore I don't want Netbeans to compile the scripts, because the software does this at Runtime. Sadly I got an exception

java.lang.RuntimeException: Uncompilable source code 
- mypackage.MyClass is not abstract 
and does not override abstract method setMetaClass(groovy.lang.MetaClass) in groovy.lang.GroovyObject

The problem is, that even with or without the Groovy-Plugin Netbeans will fail to run the project properly from IDE. Running from commandline will just work perfect.

Poking a bit around shows me the following solution for that:

• Disable "Compile on Save"-Feature: Right click and project->properties->Build->Compiling. You can also enable your Groovy-Plugin for syntax highlightning