Hi Guys I have a really strange problem on excel2010

I have the following formula for instance in cell F26
=SUM(IF($C$8:$C$16=$C26,(((F$8:F$16)*($E$8:$E$16)*8*F$4)),0))

which returns the right numeric value

when I copy this formula to the cell F27 it works great. Then I realized that in formula I actually wanted to change the F$4 to F4 now the formula does not return any result. IT returns the infamous #VALUE!

If I go back to F26 and also change the formula I get #VALUE!

How is this possible ??? I'm not changing anything in the calculation

Please help!

thanks joe