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'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).