I am also having this same problem with the current version 6.5.  This is what happens.

 

I have created a custom drop down list and added it to the editor.  This drop down list posts back, adds text to the edior, and enables or disables buttons based on the value of the drop down list.  If I remove the code which disables and enables buttons, the drop down will continue to post back.  If the code is added back, the drop down will only post back once...any subsequent post backs are lost.

 

Has any one found a solution for this problem?  I really need to disable the save button based on the permissions of the file that was chosen by the user with the drop down.  Currently, I cannot do this because of the post back problem.