Given that you've been editing, is there any reason for answering 'no' at the save prompt? As for the text boxes, they shouldn't be a problem - there's no particular limit on how many you can have - see: https://support.microsoft.com/en-us/kb/211489.

That said, it's possible the document has acquired some for of corruption. Corrupt documents can often be 'repaired' by inserting a new, empty, paragraph at the very end, copying everything except that new paragraph to a new document based on the same template (headers & footers may need to be copied separately), closing the old document and saving the new one over it. Similarly, corrupt tables can often be 'repaired' by converting the tables to text and back again or by saving the document in RTF format, closing the document then re-opening it and re-saving in the doc(x) format

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]