Occasionally Visual Studio 2010 will stop responding to most keyboard input. I've had this happen to me several times already on different machines while working on the same solution. It's only C# code. I have both ReSharper and the Visual Studio Productivity Tools installed. Some input, however, is still processed. Here are a few examples:
Writing any letter, number or symbol in the code editor.
Navigating through the source code using any navigation key (Arrow Up, Page Down, etc).
Navigating the Solution Explorer using navigation keys.
Changing properties in the Properties panel.
Typing into the search textbox in the "Standard" toolbar.
All common hotkeys I tried (F5, F7 for Start Debugging, Build Solution)
Neither copying (Ctrl+C) nor pasting (Ctrl+V)
ReSharper Alt+Enter hotkey
ReSharper Ctrl+Alt+Shift+Up and Ctrl+Alt+Shift+Down
Alt+F to open the File menu (all menus can be navigated like that, however, arrow keys do not work)
Entering characters through Alt+NumPad combinations.
The Forward/Backward buttons on my Natural Ergonomic Keyboard 4000
The only way (I know of) to resolve this, is to restart Visual Studio.