Formula lost from cell and only value retained Excel 2010

I have at least to cells, formated as currency , locked and hidden.  Each has a formula that produces a correct value.  On save and re-load the formula is gone and only the value (still the originally correct one) is in the cell.  Any ideas on what causes this and how to prevent?

cell 1 formula:  =ROUND(IF(DHSConversionRateOKed,MAX((dhsEWBudgetCapConversion),(DailyNFRate*365/12)-VLOOKUP(IF(ISBLANK(CLServiceDate),TODAY(),CLServiceDate),MedicaidMaintReq,2,TRUE)),MIN((dhsEWBudgetCapConversion),(DailyNFRate*365/12)-VLOOKUP(IF(ISBLANK(CLServiceDate),TODAY(),CLServiceDate),MedicaidMaintReq,2,TRUE))),2)

Cell 2 Formula: =ROUND(xlsProposedCLRateAdjustedforDaysAbsent,2)

Precedents are ok;  These had been control sources for form text boxes, though other cells that are control sources and had formulas did not loose their formulas