I just had same problem and after some search here's how i solved it:
- open a terminal
- cd .rtcom-accounts
vi accounts.cfg
find the line profile=jabber in the facebook account section
change it to profile=facebook-chat
save and exit
reboot

For me it worked, so far so good.

Edit:nope, after the reboot all the contacts have to be merged anyway
Edit2: i tried facebook migrator but it definitively broke the connection between contacts. In the end I resigned, deleted the old jabber account and created a new facebook account. 252 contacts to merge in next few days, though...