If you have any students who are unable to access tests with the desktops, direct them to the laptops or even the thin clients. Come to find out that the combination of XP, IE8 and the newest version of the lockdown browser that is installed on the desktops, is most likely causing the problem. I was told that when Blackboard changes in May, it will clear up the compatibility issues that currently exist (although obviously not for XP machines).