Envelope printing from Phonebook

Windows Vista with Ecco 4.01 (no EccoExt).  I occasionally print 
envelopes direct from the Phonebook, and although it can be a bit 
fiddly, I've usually been able to work it out.

But now I have a new HP Photosmart 5520 printer -- that worked fine 
initially but now some envelopes come out blank.  The envelopes are 
different sizes (yep, you guessed it -- Christmas card time) and I print 
individually using Print Setting 'Envelope: Selected Name(s)' and a Page 
Setup appropriate for the envelope size.  The expected layout will show 
in the Preview and the envelope feeds through the printer, but nothing 
prints.  I cannot figure out any common factors -- I printed one 
envelope successfully tonight, then tried to print exactly the same one 
with the same settings and it came out blank!

I'll continue exploring the possibilities, but I wonder if anyone else 
has struck a similar problem or can suggest a possible solution.

Lindsay Graham
Canberra, Australia