Really can't see any other reason for this happening unless you have unstable internet.

There is something wrong with your portforwarding if limewire has that brickwall there.

go to tools>options>advanced>firewall config

Make sure you have chosen manual port forward and type in the port you have forwarded in your router. Limewires listening port has to be the same number.

BTW did you try restarting limewire after disabling UltraPeer status? Might help

Also have you allowed limewire.exe in your windows firewall ?