Testing and QA

I am having trouble with my quiz and I'm not sure if the "secure" window is the culprit.  I had several students take the quiz multiple times and each time they submitted they would end up with a "failed to save quiz attempt" error.  I cleared their scores and tried to take the quiz myself on the same computer with the students' accounts.  I had no problem completing the quiz.  I suspected, but I can't confirm, that the students were using forbidden keystrokes or switching windows.  Would this cause an automatic failure?
Another related problem is: in a couple of large classes taking the quiz in a lab I had about half of the students get zeroes on a 20-question quiz.  They all complained that their selected answers were being erased.  I cleared their scores and let them try again.  I found that the students who did not submit before the time-limit was reached were getting zeroes, regardless of any correct answers.  When I practiced the quiz on my own computer, using Firefox 1.07, the timout caused the proper response of automatically submitting my current responses.  The labs are equiped with IE 6.  What is the intended behavior of timing-out on a quiz?