I've had this issue before but not recently, until tonight when it re-occured.
I added one of my Jitsi accounts (my own domain but hosted on gmail)
as a contact in Gibberbot earlier and now the Gibberbot contact
(gmail.com) is showing twice in Jitsi (both showing the contact as
online) but it may just be a co-incidence as another of my contacts in
Jitsi, not added to Gibberbot, is also showing twice and both as
offline. I can't say when exactly this started either, so it may have
been some time after I added the contact in Gibberbot.
I've tried closing Jitsi and restarting it but it still shows those
two contacts twice each.
I'm using 2.3.4656.9728 on Win7 x64.