Please describe the problem:
Sometimes, when I click on the main menu button, the main menu appears in a strange way. See the screenshot.

Steps to reproduce:
1. Click on the main menu button in the panel.


Actual results:
The main menu appears in a strange way. See the screenshot. 

Expected results:
The main menu should appear as it normally does

Does this happen every time?
No. It only happens sometimes. I have not been able to determine any way to get this to happen on purpose, but it always seems NOT to happen the second time I try. That is, if I click on the menu button and the menu appears in this strange way, I can click on the desktop to dismiss the mutant menu. When I click on the main menu button a second time, I believe it always shows up correctly.

Other information:
Once I have clicked on the main menu and it comes up looking odd, I cannot take a screenshot using the Print Screen key on my keyboard. So, these screenshots were taken by aiming a camera at the monitor.