gnus server and network problem

[Leon]

Hi there,

I just met this annoying problem. I brought my laptop to use a guest
wireless network which blocked news.gmane.org, my news server. So the
server went offline.

Later when I come back to my home and use my usual network, I won't be
able to use news.gmane.org in the same emacs. Gnus will always show
that it can't connect to server.

Finally I have to restart emacs to post this message in gnus.

Since I will be moving around quite often, I'd appreciate if you know
a fix to this issue.

Thank you.
-- 
Leon