class cast exception error while editing operation parameters

When attempting to create a new handler, I've forgot to check the event type and got errors in the creation handler wizard. But once I've fixed the parameters, I've obtained duplicate automation chains.

So, in automation chains list, I've deleted the duplicates and started to edit the chain. I was able to add operations in, but once I've tried to save an operation parameter, I've got the an error occured about a class cast exception, dialog with obsfucated classes listed.