Counting the number of commom non-blanks in two rows

[Narf <narf mundo-r com>]

Hi.

Since I've upgraded gnumeric to 1.8.x, the formula I used in gnumeric
1.6.x to count the common non-blanks between to columns doesn't work:

=sum(1*not(isblank(A1:A50))*not(isblank(B1:B50)))

This used to give as a result the number of rows for which A and B have
non-blank values. Now the result is always 0 or 1, depending on the
columns I choose.

Is this a bug or the correct way for isblank to work? If it's not a bug,
is there any other way to obtain the result that I got with gnumeric
1.6?

Thanks.