The easiest way to restore ACA is from Windows start menu, under All Programs->Autodesk->Version Folder, select Reset Settings to Default. Warning, any customization you did will be lost.
For the future please start a new thread with your issue, instead of piggybacking on old threads.
___________________________________________________________________ Normal people believe that if it ain't broke, don't fix it. Software Engineers believe that if it ain't broke, it doesn't have enough features yet.