Digital BW, The Print

I am in the process of calibrating my Epson 1290 with the beta8 on Mac OS X.3.

The first print of the Ink Pattern Page prints weirdly: instead of progressive scales, I 
get kind of random densities. There are more dark densities on the left but, for 
example, the 40% path of ink 6 isquite dark, then the 45% patch is much lighter and it 
goes up again until the 60% patch which is the same density as the 40%, etc.. All the 
inks behave in a similarly random way.

What do I do wrong ?

Thanks.