I\'ll be coding along in Visual Studio 2008, and eventually I make a mistake. I press CTRL - Z to undo and NOTHING HAPPENS. I\'m not talking about anything
I had the same problem recently. I think it was caused by an exception in ReSharper (these are shown in the status bar of Visual Studio), at least ReSharper showed a message box to submit some errors to JetBrains at around the same time.
If you experience this problem again, verify whether ReSharper shows any errors/exceptions, and if it does, you might want to submit them to JetBrains.
After restarting Visual Studio, undo worked again (for me).