I have sent an error report and examined the details of the error shown in the popup window announcing the error. The first few lines of the error report were as follows: Executable Path - /usr/bin/compiz Package compiz-core 1:0.9.12.2+16.04.20160823-oubuntu1 Crash//compiz crashed with SIGSEGV .top_unity_support_test.0
Consequences of the crash: Restarting the computer just comes up with the internal error message. The launch bar has limited function. The DASH does not work, so I cannot bring up programs such as UPDATE. I can bring up other programs on the launch bar; but when the pointer goes back and forth between desk top - with whatever program is running on the desktop (e.g., firefox) - the screen blanks to the empty back ground and then the display comes back. When I try to shut down the the computer via clicking on the shut down line is the menu in the upper right corner of the screen, it will not shut down. The only way I can shut things down is by manually pressing the power button on the computer.
Some possibly useless information:
This is a dual boot machine with Windows XP in the other partition. The windows partition seems to be working OK (knock on wood).
I recently installed Oracle's Virtual Box and have been trying to configure a windows XP guest. So far it has been a lot of trouble and possibly may lie behind my problems.