Cannot move, hide, or add anything in SharePoint navigation menu

Yesterday I have witnessed a very weird behaviour of SharePoint navigation menu. Basically, SharePoint refused to save any changes (add/remove, hide, move, etc.) to SharePoint navigation menu. To make things even more confusing, it did not throw any errors or warnings in the event logs or SharePoint logs when this happened! In the process of troubleshooting this problem, we have systematically eliminated navigation provider(s), master pages, pages layouts, web.config(s), etc. as a potential source of this problem. We have checked everything and we're not able to come even close to finding a solution. Just before we started to plan on rebuilding the entire SharePoint environment to solve the problem, we have (almost accidently) found what was causing the problem. It turns out that what was causing this weird behaviour is that a default value of a single Boolean variable (_spSuppressFormOnSubmitWrapper) in INIT.JS file was changed from FALSE to TRUE. This almost makes sense, but... If you change the default behaviour of the submit button, shouldn't this change for effect the entire SharePoint environment, instead of singling only the navigation menu? Weird?! I am glad the problem was resolved though J