This may, or may not be, all the fault of the users.

I've found that for some strange reason certain programs in Win 7 x64 amazingly enough sometimes load the dialog window onto the screen UNDER other windows, and not on top as modal. It is somewhat madding. One if these that I use that does this is what prints pdf documents.

But having said that I agree with the other A above that this is a training issue.

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However, I can imagine a looping script in PowerShell which gets run as a background job, which regularly checks for certain tasks on certain workstations, and for how long they have been active and possibly idle, and kills any such process. But it's not a very good solution I don't think, because it might break other things. :-( You know what is said about Engineers, that they don't solve problems but rather trade one problem for another.