I have built a very large and complex financial model (around 5mb file size)
and am having problems with cells not updating. This has nothing to do with
iterations being switched on/off or with circularity (i have tested for this
- calcs are set to auto and I have hit F9 a million times when i switch to
iterations, also there is no circularity). It only seems to happen once the
file becomes very large or the model particularly complex (this one is 50
work sheets with average 80 cols and 100 rows)

When I save the file as a new version, the cells all update. Also, when I
re-copy the formulas, they update. It is very very bizzare... Has anyone else
had this problem and if so what did you do to fix it?