IF Formula not giving expected results.

I have a column that gets dollar amounts added to it via data import (892.38 as an example). Another column has the following formula in it that I'm having a hard time with.

=IF(AO4=0, AW4, AO4)

basically if the value is not a zero, then set the cell with formula equal to that number. If it is a zero, then set the cell's value equal to the value in cell AWxx.......

The data gets imported fine, and the formula works for cells where AOxx has a non zero value. For cells with a value of zero, it returns zero to the cell with the formula.

The odd thing is that when I click in one of the AOxx cells with a zero value, and click up in the formula bar, then click out of the cell, it evaluates the formula properly and returns the value in column AWxx because the value is now equal to zero.

This is very strange to say the least. I was beginning to think my data import was padding a space to the front of the zero value in column AOxx........

so...how do I get the formula to evaluate as it should without having to click in each cell of column AOxx that has a zero value in it?