Slow on some PCs

[JKnight]

Hi guys,

I have a worksheet that has some data validation in it. It inexplicably (to me) runs much slower on some machines than others. Does anyone know why and is there any way I can fix it? I have put the details below:

Any help much appreciated!
Jonny

Created in Excel 2007
Saved in Compatibility mode
All data validation is on same sheet
The machines on which it works fine are no newer or higher spec that those on which it doesn't work so well
There are no macros or other complications on the sheets
I'm confused!