array formulas

[daxi]

I tried to convert an existing set of sheets from excel 97 to SO7.
I ended with some hundreds of "Error 504". Im working now for hours
with no remarkable success to find out, where the reasons are.
My biggest problem seems to be in some array formulas. Whatever I
found in this group sounds not too hopeful. Is there anybody knowing
"The Solution?

Example:

A B C

1 F A 5
2 C A 5
3 D A 10
4 F B 15
5 C B 20
6 D B 25
7
8
9 C A
10
11
12 Err:504

The result should be 5, but I got only errors 504

Examples (4 of dozends) for A12:
{=SUMME(WENN(A9=$A$1:$A$6;WENN(B9=$B$1:$B$6;$C$1:$C$6)))}
{=SUMME(WENN(A9=$A$1:$A$6;WENN(B9=$B$1:$B$6;$C$1:$C$6;"a");"b"))}
{=SUMME(WENN(A9=$A$1:$A$6;WENN(B9=$B$1:$B$6;$C$1:$C$6;"");""))}
{=SUMME(WENN(A9=$A$1:$A$6;WENN(B9=$B$1:$B$6;$C$1:$C$6;0);0))}

Thanks
daxi