I'm having a similar issue. That happens right after you open a ticket for ~1 second and then corrects itself. If you click the assign button, it does it again and then gives a message on the ticket.
There is another issue I'm having where a message box pops up and says the ticket is locked and asks if I want to proceed.
This started happening after I upgraded to php 5.3. There is only a deprecated function notice in the php error log. Anyone know of a fix?
:(