Recently, there have been a few cases where students click to submit an answer in Sakai (on their personal computers) and the page simply freezes.  The same link works on other machines.  It was discovered that BitDefender was loaded onto the computer and was causing this issue.  Since BitDefender is at end-of-life anyway, we encouraged the students to uninstall from their computers, which (after a reboot) immediately fixed the Sakai issue.