A THREAD on Google Group microsoft.public.excel reveals that Excel 2007 loses its grip with arithmetic that involves the number 65,535.
Several examples are shown, perhaps the simplest of which is the calculation ( 850 X 77.1 ), which should produce 65,535 but instead returns 100,000.
2^16 - 1 can't be a coincidence.
(It works fine on Excel 97.)
The thread is [link|http://groups.google.com/group/microsoft.public.excel/browse_thread/thread/2bcad1a1a4861879/2f8806d5400dfe22?hl=en#2f8806d5400dfe22|here], it lists lots of other examples (and is an interesting read).
Cheers,
Scott.