It's the old adage of "what's changed?" Something must have. If it is suddenly not working look to make sure anti virus is not quarantining anything, windows updates aren't deleting anything and if using office 365 make sure it is not automatically upgrading excel to an incompatible version .

Hey Peter. No idea, but if it's any help they can have 50% off FRS. Cheers John

I peeled off all the Excel updates and that didn't fix it. I am not sure how to determine if the XLA and XLL files got "corrupted" by the antivirus or some other way, but it looks like that might be the case. 

Thanks, but then we would have the problem of rewriting the forecast spreadsheet and several other spreadsheets to work with FRS, which I can testfiy has been problem free on other sites. 

No worries. We can do that for you if you like. Rewriting is pretty easy as FRS uses the same financial functions and fields as FR. (Eg: FRAMTA NETYTD in FR is FRAMTA NETYTD in FRS). 

OK, so I forgot to mention, the whole site was done as a workstation install where the programs are on \\server\sage\programs

If I uninstall on a workstation and reinstall from the DVD to the C drive where the programs are on C:\sage\sage300

the FR reports work. They used to work from \\server though. So, maybe a firewall issue? Also there is a know problem with Excel where the UNC paths get changed automagically in a spreadsheet, so if you map a share one day, run excel and then unmap it, and reference it by UNC it doesn't work even though nothing has moved. 

I can install on the C drive for the few users that want FR, but it seems like a workaround and not really fixing the problem.