Starting and stopping the explorer fixed the problem for me.
For inexperienced users:
- Hold Ctrl+ALT+delete at the same time.
- Select "task manager." Choose the "Processes" tab at the top.
- find "windows explorer" in the list (near the end) and click it.
Click the "restart" button in the bottom right side of box --- OR right click "Windows Explorer" and click "end task" (don't panic when you can no longer see your desktop or windows)
Just hold Ctrl+alt+delete again, click task manager
- then click "file" at the top, select "run new task," then type
explorer.exe
Your desktop will re-appear (possibly re-arranged and you may need to re-organize your icons the way you desire).
But after that, the programs should again be working properly and allowing the charms menu and other program menus to appear as they did before.