Data validation error with multiple CPU

[Yorkeyite]

Excel 2010 running on XP question, I have a formula based validation dependent on a calculated value in another cell that fails when more than 1 processor is used. The failure is not consistent though, works for a while then falls over. I presume that the data validation formula is being picked up by one thread and the cell it is dependent on is picked up by another with them getting out of sync. Data validation checking shows an error after the entry is made.
i.e. same computer, 2 processors running, it fails, reduce to 1 in options everything is OK, it is a complex spreadsheet and I would like to run multiple processors, is there any way around it?

 

[Yorkeyite]

You do not provide enough information to tell what the problem is.



What service pack of XP? 64 or 32 bit?

What is the data validation formula?

What data is present (in all precedent cells) when the error is shown?

The spreadsheet is a roster, Names for row headers and dates for column headers, it counts the number of like entries in a column and the validation stops further entries when a limit is reached.
The Validation is formula based that requires a referenced cell to be TRUE to allow the entry of that code

Referenced cell=TRUE
=E296=TRUE
The Referenced cell is an AND statement.
=AND(LEFT(E8,1)<>" ",RIGHT(E8,1)<>" ",COUNTIF(E$8:E$41,$B$156)<=E$214,COUNTIF(E$8:E$41,$B$157)<=E$215,COUNTIF(E$8:E$41,$B$158)<=E$216,COUNTIF(E$8:E$41,$B$159)<=E$217,COUNTIF(E$8:E$41,$B$160)<=E$218,COUNTIF(E$8:E$145,$B$166)<=E$224,COUNTIF(E$8:E$145,$B$167)<=E$225,COUNTIF(E$8:E$145,$B$168)<=E$226,COUNTIF(E$8:E$145,$B$169)<=E$227,COUNTIF(E$8:E$145,$B$170)<=E$228,OR(COUNTIF(ShiftCode,E8)=1,ISBLANK(E8)))

It does not fail at any particular time it is a random event, it does not fail at all if I reduce the active processors to one.