I suspect we are dealing with text imported from another program or the Internet here.
Ctrl+Shift+Space inserts a hard (non-breaking) space, one that does not allow normal wrapping of text between words. If all of your spaces are non-breaking, Word has no choice but to chop text up.
- Open a COPY of your document.
- Press Ctrl+H to bring up the replace dialog.
- In the find box, press Ctrl+Shift+Space.
- In the replace box, press the space bar by itself.
- Click on Replace All.
What happens?