Okay I was playing around with another script today and noticed the stepbackward script in my file menu/scripts...totally forgot about this due to the previous error. So I select it from the menu and it works fine, but if I assign it to a keyboard shortcut that's when the error comes up...
btw, if you want adobe to officially fix this problem, show your support and help request for this fix in the adobe forums topic linked below... Make "step backward" command maintain current layer selection (like the "undo" command's behavior)... http://forums.adobe.com/message/3395997#3395997