When GroovyParser.clearCache() is called (when a project is closed or a Full build is invoked), all URLClassloader in the parent hierachy are closed including the System Classloader.

It leads to errors when the application try to load classes from the JRE like the crypto classes.
The side effect is that it is no more possible to fetch a git repository by example, you get exceptions like

java.security.NoSuchAlgorithmException: SunTls12RsaPremasterSecret KeyGenerator not available

The GroovyClassLoaderFactory should filter the Classloader.getSystemClassloader() in the close() method.