A simple Excel 2007 worksheet is taking ages to accept basic chang
 

I have one worksheet (Excel 2007) - 86 rows x 30 columns, which has basic
addition and subtraction formulas in the 3 of the columns. The other 2
worksheets in the same spreadsheet document are working fine. For some
reason however, unlike all my other (more complex) spreadsheets, it is taking
a very long time to accept very basic changes, such as inputting a figure in
one cell, or changing the column widths, or font colours. For every small
change I try to make it is 'Not Responding' for at least 30sec - 2 min, which
is very frustrating. I saved the worksheet into Excel 97-2003 compatible
version and on an old laptop I have, it was working perfectly fine. Any
ideas as to why this is?