Getting this message: "This won't work because it would move cells in a table on your worksheet."

I have had the same problem but my problem was that I created a table, I didn't even realise I did, selecting a few columns (usually selected to the end of the worksheet). So when I tried to add a row, it was imposible because I already had maximum rows. Don't know how I realised that but problem was fixed by deleting the unused rows, creating more space to add them back in (anywhere you want).