Track Changes button grayed out excel 2010

I have an excel workbook (.xlsx) in which I want to track changes. However track changes button is grayed out. I tried searching, but couldn't find any solution.

This workbook contains 5 worksheets, so I tried moving (copying) each sheet to a new workbook, and I found that when I copy one particular sheet, track changes option gets grayed out in the new workbook. So there is something in this sheet which is causing track changes to be grayed out.

Larger Image

Finally I found answer to the solution. Apparently the track changes option is disabled (grayed out) if any of the sheet contains a table. There was one table in one of the sheets of the workbook. When I changed the table back to range, I was able to track changes.