g.eachError(bean: instanceName) returns error message while used in controllers

I always used g.eachError(bean: instanceName) in my controllers (and also in services) in Grails 1.3.7 and it worked like a charm. After an upgrade to Grails 2.0.0 it seems that g.eachError(bean: instanceName) doesnt work anymore.

Here the errormessage from the grails-error page / stacktrace in netbeans:

Error 500: Internal Server Error
URI: /savetest/test/save
Class: java.lang.NullPointerException
Message: null

Around line 22 of grails-app/controllers/savetest/TestController.groovy

NullPointerException occurred when processing request: [POST] /savetest/test/save - parameters:
vorname:
test: test
name:
Stacktrace follows:
Message: null
Line | Method
->> 22 | doCall in savetest.TestController$_closure2$$ENLSCNLc

• - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

  886	runTask in java.util.concurrent.ThreadPoolExecutor$Worker
  908	run . . in '' ^ 680	run in java.lang.Thread

//Stacktrace taken from the error.gsp (extended it with the whole code)
18: if(testInstance.save())

{ 19: //Save successfull, go on 20: }

else { //Constraint errors, prepare JSON response with error messages.
21: //This doenst work anymore
22: g.eachError(bean: testInstance) {
23: postResponse.errors."$

{it.field}" = g.message(error: it)
24: }
25: //This one works perfect, but seems inefficient to me
26: testInstance.errors.allErrors.each {
27: //Do Something with the error
28: postResponse.errors."${it.field}

" = g.message(code: "$

{testInstance.class.name}

.$

{it.field}

.$

{testInstance.errors.getFieldError(it.field).code}

.error")
29: }

It seems to me that the non persisted domain objects causes this error. But i am not 100% sure.