Steve - Did this solve the problem for you?
I've been experiencing exactly the same problem (on my work PC). My
colleagues all have the same problem.
My PC is running XP, and has all the latest updates (including those for
Office). The problem was dealt with by a Microsoft technician who suggested
the following (once all options relating to PC/software/graphics settings etc
were eliminated): -
COMPLETED ACTIONS TAKEN AND RESULTS:
====================
- Rebuilt calculation chain replacing all = signs with ##, save, close,
reopen, change ## to = sign
- Recreated Excel registry keys(Removed corrupt/bad icon in ribbon)
NEXT STEPS AND TIMELINE:
====================
For each workbook experiencing the same issue as listed above:
1) Make note of any array formulas in the workbook(these will have to be
rebuilt after the process)
2) Rebuild the calculation chain by replacing all = signs with ## for the
entire workbook, save, close, reopen, change ## to = sign
This appears to have solved the problem for an individual workbook. HOWEVER,
my problem can exist in a block of cells, a few cells, or just one cell.
Therefore, I need to already know there is a problem before I can solve the
problem (it's a chicken and egg scenario!). I'm still concerned since I never
know when the problem will crop up again (it happens on spreadsheets
converted from .xls to .xlsx, and new spreadsheets created in excel 2007).