Apparently I'm stupid. When I copied back the wallet backup the address came back as you said. Didn't read that in the manual... :-)

My machine crashed, the Bitcoin client database is broken, and after reinstalling the client (saved wallet before!) the old bitcoin address is gone.
That's bad since some pay-per-share mining pool owed me some fractions of a bitcoin to that address.
Is there a way to make the client use the old address again, or are some fractions of a bitcoin now lost forever due to database crash?