I suspect the error in inserting rows is because Excel believes it has data
to the bottom of the sheet (Row 65536)

To test this go to A1 and press Ctrl+End.  If (On your troublesome
workbook), this goes to row 65536 then that is the issue.

To correct:

Click in the row header (The grey square with the number on), for the first
row below your actual data. Now scroll to the bottom of the spreadsheet and,
while holding down the shift key, click on the row header for the last row
(Probably 65536).

Now right click on one of the selected row headers and select 'Delete'.

Save the workbook (Very important).

All should now be ok