To find out if your user preferences are, back up your preferences using the tool options, then reset and check if this problem fixes. If so, then you can slowly restore the old settings of 1 partition at a time to find out what causes the problems. At this point, you should reset and restore all those that worked again.
I had to do this once when the find / replace dialog disappeared. If I used a short cut or menu, a dialog should appear on the screen. Doing the above resolved the issue
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