I have been typing up my notes for classes throughout the semester (=lots of hours) and yesterday after saving my file, I closed it and upon trying to reopen got the message:
"there are problems with the contents"

After looking for details this message appeared:
"the name in the end tag of the element must match the element type in the start tag"

I tried downloading OpenOffice and using that to open it, but only 10 of the 33 pages were there and all of my equations were gone.

Can someone please help me to be able to access my file!?