You are right. I messed up these two terms.

"不要把TREATY和exempt personal联系在一起?"

You are right. I messed up these two terms. "You will not be an exempt individual as a student if you have been exempt as a teacher,trainee, or student for any part of more than 5 calendar years unless you establish that you do not intend to reside permanently in the United States and you have substantially complied with the requirements of your visa."(publication 519 Page 7)

It is very clear now that I am no longer "an exempt individual". As you said, I should be qualified as RA for the entire 2005 and also for treaty exempt. The IRS officer may not know the detail of saving clause of Atricle 20.

Thanks very much, stp!