"Undo" feature in Visual Studio 2008 stops working

I've come across the same issue - and I too use VisualSVN and ReShaper. What version of ReSharper are you using, 4.5.x?

I've found it appearing with 4.5.x but a recent EAP build (I can't recall which) did address it for me after I reset the Keyboard layout in Visual Studio.

So first as others have stated, try disabling ReSharper (Addin Manager, until startup too) restart (the IDE) and see if it appears whilst your working (after resetting the keyboard layout).

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).

If the other solutions don't work

I think a common problem is that keyboard bindings get changed somehow. It's easiest just to go and reset them like this:

• Reset them. Tools -> Options -> Environment -> Keyboard -> Reset -> OK
• Restart Visual Studio

I have observed that the undo option is being disabled when I press CTRL + ENTER accidentally, and I fixed this by removing this hotkey.

To do this go to : Tools -> Option -> Environment -> Keyboard and remove Edit.LineOpenAbove shortcut.