What behavior on which system to you consider to be buggy? On 3.3.1, Win 7, all seems fine.  By selecting Windows as a component, you imply that something is wrong on Windows.

"on Windows, not only can the user continue to write[(if the user Cancels),] it is possible to try to close the window again. Each time the user attempts to close the editor the "Save on Close" window appears one more time."

This is what should happen.

"Also, when you have 2 such windows if you say 'no' then,no matter what the answer to the second window is, IDLE crashes."

I do not see this.

'with Python 3.3': 3.3 is a version of the language. 3.3.0 and 3.3.1 are two different patch releases. Did you use the latter, which has several Idle improvements? When discussing bugs, we need to be specific as to releases used.