It seeems that the Extended Choice Parameter Plug-In [tried version 0.64] and Jenkins ver. 2.0 don't work together.

When I create a simple groovy script for the plugin and I try to launch the build it appears the message:

"You have unapproved groovy scripts that need approval before they can be executed. Go to In-Process Script Approval page to approve your scripts."

However in the approval page there are no scripts to be approved. See attached screenshot for the reference script I used.

If the script is modified in the build configuration page, it is appearing correctly as a script to be approved. However approving it, will still display the message

"You have unapproved groovy scripts that need approval before they can be executed. Go to In-Process Script Approval page to approve your scripts."

This happened after the upgrade to Jenkins 2.0 from Jenkins ver. 1.656