This is about the upstream bug http://developer.pidgin.im/ticket/4458 when connecting to a jabber server using SSL/TLS. (I have the gnutls USE flag enabled).
The error message is:
"Invalid certificate chain
The certificate chain presented for <hostname> is not valid."
Some discussion about this is here too (in German): http://web.jabber.ccc.de/?p=29
I fixed it doing the following:
added the line
in src_compile() in net-im/pidgin/pidgin-2.5.1.ebuild before "if use gnutls ; then ..."
ebuild /usr/portage/net-im/pidgin/pidgin-2.5.1.ebuild digest
ebuild /usr/portage/net-im/pidgin/pidgin-2.5.1.ebuild manifest
emerge -v pidgin
Sorry if this is not the cleanest way.
I have a similar problem with pidgin-2.5.6. One developer told me that this could be because the gentoo ebuild doesn't set the certificate directory option: --with-system-ssl-certs=/etc/ssl/certs
Reading upstream bug report this problem is completely resolved in 2.6.2 and we have 2.6.3 stable now, so I guess this bug is closed. Any way, thank you for report, guys.