Just updated one of my Ubuntu servers to Oneric, and I noticed some error messages during the installation:
error adding /etc/ssl/certs/brasil.gov.br.pem error adding /etc/ssl/certs/cacert.org.pem error adding /etc/ssl/certs/ca.pem ...
I found a solution in this forum post:
$ sudo dpkg-reconfigure ca-certificates
…and select all certificates in the dialog.
(To be honest, I don’t know if the error actually caused any problem for me, but it’s nice to have preempted any problems now that I have the error messages fresh in mind.)