I have a spreadsheet that is approx 7.5M. I have been running with this noe
for several months with no problems, it does not contain any macros, only
formulas such as Vlookups and som pivot tables.

Yesterday it started doing strange things!

Everytime I enter lines, filter, delete line or even input data it freezes
and at the bottom left it says 'calculating cells' with a %. This process
takes approx 20 seconds but is happening all the time.

As you can appreciated I can not get things done quickly as it is slowing me
down.

Can anyone shed any light on why this may be happening and how to stop it.

Thanks