Chart not updating

Hi,
this is a new one for me!
Excel 2007 combo chart, 1 series column, 3 series line
values are changed by formulas dependant on various dropdowns and all formulas update.
Problem:
The charts (5 of) have stopped updating when the data changes.
F9 makes no difference.
If I reselect the same data source it updates
Also the chart titles are linked to formulas and these have also stopped updating. If I select the formula bar and enter the title will update.

Unfortunately I cant upload the workbook its in, a its too large & B confidential.
Tried opening a new workbook, using the same values as a data set, recreated the chart and all works fine when updating values.

Found various references to this problem on the net, all end up using a macro to make a change to the chart to update it.
I have done this using Worksheet change event however this doesn't updaye all the chart titles.

Anyone got any idea of the cause of this?

Calculation Options switched to automatic?

yes calculations on automatic,
however that shouldn't stop F9 from recalculating. as I mentioned all the calculations are working when drop downs selected, just the charts are not updating

Yes, you're right.

I really need an example posted to see the behaviour.

Cold you post an example with a small dataset of dummy data?

Very strange this. I spent hours trying to resolve this problem.
Got fed up, turned pc off for the night.
turned it back on in the morning and all was working fine.
Hasn't happened since.

There's a few hours of my life I will never get back!