I set up a server (centos, apache) and almost everything is ok.
on any course when the user attach a file and go to the screen with the message
"Are you sure you want to submit your work for grading? You will not be able to make any more changes"
and click on continue, for that user the page never reload, get stuck there, nothing happen, don't have any get or post on firebug, just freeze.
for the user access anything he has to close the browser and login again.
nobody has seen something like that?