negative balances not permitted

Hello. I am having trouble adding multiple numbers within a cell. For example if I enter =60+40,instead of seeing 100 in the cell, I receive an error message ‘negative balances not permitted’. This is very confusing as a) the answer is not a negative value, and b) even if it was a negative, it should read as one in the cell. I am getting the same problem throughout the spreadsheet, which is a cash flow forecast. The formatting of the cells is set to currency.
Help would be appreciated. I have a deadline.


That certainly was a validity check or macro designed into the spreadsheet document, not a Calc message.