Excel 2007 : Formulas across sheets not calcing??

Hi,
I've been working on a workbook for weeks and all of a sudden my workbook won't calculate properly - specifically, it won't calculate formulas which refer to data in other sheets within the workbook (either on manual calc or auto calc) - it will calculate the result of a cell if I hit F2 then Enter on that cell, but won't do them all automatically.

The things that I have done today (which could have possibly caused the issue to arise I guess) are:
- Created some macros to lock worksheets when the worksheets are activated (but to allow the user to expand/contract groupings by using the "enable outlining" code - refer below, maybe its this macro creating the issue but I don't understand why).
- Created the groupings referred to above.
Or it could obviously have been something else that I've done that I can't think of.

Can anyone suggest why this is happening, and more importantly, how I can fix it??

Incidentally, the macro referred to above was suggested by someone in a forum - in order to resolve my issue whereby I want the file user to be able to hide/unhide rows and columns but with the sheet locked - its not an elegant solution because I want them to be able to hide/unhide rows independently of each other which are directly adjacent to eachother (however I can't group individual rows on their own when they are adjacent to eachother - they just turn into a single grouping). Any ideas on how I would deal with this separate issue would also be appreciated.

Private Sub Worksheet_activate()
Protect Password:="", UserInterfaceOnly:=True
EnableOutlining = True
End Sub

Cheers,
Thackers

By setting EnableOutlining to False, the issue seems to have disappeared.

But of course, this means the user can no longer use the grouping functionality so I am back to square one. I will add a post looking for a solution to this problem