unison ssh issues

for some reason (when having trouble with home PC and when setting up a new one) unison in gui mode just sits there at 'contacting server'.

Run unison in text mode and the command line will ask you if you want to add the RSA key fingerprint (funny, I thought that had happened through the gui previously?)

boot@terver:~/.unison# unison -ui text crossing_groups_sync.prf
Contacting terver...
The authenticity of host 'xxx.xxx.xxx.xxx (xxx.xxx.xxx.xxx)' can't be established.
RSA key fingerprint is xxxx
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'xxx.xxx.xxx.xxx' (RSA) to the list of known hosts.
boot@xxx.xxx.xxx.xxx's password: