Try Jabber site: jabber.sugarlabs.org instead of jabber.laptop.org .
Nobody seems to be using the laptop.org site the last couple of days (or it is no longer active ?) and the sugarlabs.org site has consistently shown several XO's.
Also, the ports used are 5222 or 5223 for the protocol used by the XO (actually the XO just uses older 5223). I would not suspect your router is blocking these ports --- but check.
If you want to try other jabber sites, checkout:http://wiki.laptop.org/go/Community_Jabber_Servers