Problems using the SUMPRODUCT function

I was reading this thread

http://www.excelforum.com/excel-form...our-block.html

where FDibbins used SUMIF to solve the OP's problem.

Curious to see if this was solvable using SUMPRODUCT I had a go at it but the result was rather disappointing. Two results correspond with what is expected and at least three results are wrong.

Unable to see what the problem is I hope some forum member may solve this.

Alf