Running a Windows 7 64 bit VMWare 8 guest on a Windows 7 64 bit host.
The buttons disappeared from all programs, this is not the case of F11 on IE.
This happens in a virtual VM machine (so probably not an issue of a graphics driver). Other VMs are not affected, nor is the host.
Opening the context menu on the windows' title bar shows Minimze etc, and it's working.
Recent configuration chages - Adobe reader and flash player updated about a week ago. I don't think this could have caused the problem, as I've only noticed it today.
Only suspect: Yesterday the internet was very sluggish, and a support person made me click "Restore advanced settings" in IE. The problem, however, appears in all applications: Office, notepad (see picture below), anything I checked.