Please read https://bugs.launchpad.net/ubuntu/+source/gnutls26/+bug/418935 for a full explanation
Essentially, pidgin is able to connect to Webex Connect's jabber while Empathy is not. This is due to problems in telepathy-gabble.
Anyway, here is what I'm running that has the problem:
$ cat /etc/fedora-release
Fedora release 14 (Laughlin)
$ rpm -qa | egrep "telepathy-gabble|empathy"
Please make this work... I hate pidgin :-)