login Problem In terminal server 5.2 win server 2003

I am running windows server 2003 AD+Oracle+Nat+terminal server its running since last 2 years smoothly but last 20 days when second terminal client trying to connect server authenticate the user and while loading profile the whole Remote desktop windows disappear its only happens when 2nd client trying to connect other wise 1st session running smoothly.if you have any idea plz share it.