Actually, the count function will return how many cells have numeric values, but not actualy the sum of all the numeric values.
I tried just using the sum() function and this example worked for me.
My row example had the following:
A1|B1|C1|D1|E1
1 | 1| test | 1| 1|test
When you apply the formula =sum(A1:E1), the value returned was 4.
Reason being is that when an argument is an array or reference in the sum() function, only numbers in that array or reference are counted. Empty cells, logical values, or text in the array or reference are ignored.
Give that a try and see if it works for you.