For one (and only one) execution group (on a worksheet with many execution groups, both before and afterwards) which was modified by a student but which looks perfectly fine, a right click on any selected text causes Maple to hang (before any context menu appears). When I look at the mserver.exe process on Task Manager, it continues to use 99% of the CPU and keeps increasing its memory use. In other words, some non-visible part of the parsing information stored by Maple on the worksheet for that execution group seems to have sent the mserver into an infinite loop when it tries to isolate the selected text for processing. Of course, the halt calculation button doesn't function in this case. The hangup can only be stopped by having Windows bring Maple to a forced stop.
This brings up the fact that it would really be useful if there was a toggle tool button to unhide/hide non-visible parsing/editing/formating codes and allow editing of these codes directly if necessary.