It is a xml error for some reason may be because of deleting a view or string in another view or may be for missing " or /> ..... etc
But here I am using a good technique to figure out where is the problem exactly :-
I know it is not the solution of the main problem but it will make you find where is the error quickly and save you time.
Update
There is another way you can find out easily, as Bennik2000 write in comment, you can look at the right scrollbar for red lines, they also indicate errors.
Update
I found a very simple way to get where is the error exactly if it is in resource file or even java file.
1- Go to Project Window.
2- Open the file that has the error.
3- Click F2 to go to the nearest error appears (it will go to the correct line)