Briefcase update corrupting formulae

I have been using Briefcase to transport Excel Workbooks for many years but recently I have found that after updating the parent file with briefcase that has been worked on, there are a number of conditional functions that return a wrong logic result. for example IF(COUNT(B$5:B$34)=0,"-",COUNT(B$5:B$34)) which I am using to count the number of entries in column B returns 'False' when there are entries in the column and so the result is erroneous. The same formula on my master copy of the workbook returns 'True' for the entries and the result is correct. Copying the formula from the corrupted updated file to the master file makes the master return an erroneous result. There are other formulae that are corrupted in the updated file. I don't know whether it is the briefcase or a compatibility problem with Windows. I am running Windows 7 and MS Office 2010, but have never encountered this problem before.

If anyone has an idea as to what is causing this and how to rectify the issue I would be most grateful.

It is me again. I have inadvertently discovered that the problem all stems from the date entries, and when I re-entered the dates, or double-clicked the date entries the formulae did not return an error and worked normally.
It was not a case of the 'formatting'. It is still a mystery as to what caused the problem that the dates were unrecognisable to the formulae until they were re-entered?