Startup issues and server availability

Hi all,

i've recently made the move to Gnus from slrn - overall, i've found
it to be much more enjoyable to use.  However, i'm finding some
hassles:

* Earlier today, whilst starting up Gnus, an ethernet cable got knocked
loose, and so Gnus quite rightly decided the server was unavailable. i
thought that i could let Gnus know that my news server was again
available by visiting the server buffer and pressing 'O' whilst on
the line listing the news server i use. Nope, didn't work. i tried
quitting Gnus (via 'q' from the Group buffer) and restarting it,
but that made no difference either. The only thing that seems to work
is restarting Emacs entirely.

* i can't work out how to get the same sort of startup performance
from Gnus as i get from slrn. When i start up slrn, there's a pause
of only a few seconds before i get a listing of my subscribed groups
and the new article count for each group. Using Gnus, however, i first
have to wait whilst the entire active list is downloaded - ~2.5M on
the news server i'm using, news.bigpond.com - and then my CPU usage
jumps to 100 percent for a few minutes whilst Gnus finds new news. i've
spent a fair amount of time playing around with what i presume are the
relevant settings in ~/.gnus (which i've confirmed is the config file
Gnus is looking for), without success. Currently that file looks like:

(setq gnus-check-new-newsgroups 'ask-server
      gnus-read-active-file 'some 
      gnus-use-cache t
      gnus-cache-directory "~/.News/cache"
      gnus-cache-active-file "~/.News/cache/active")

But it doesn't matter what values i give to gnus-check-new-newsgroups
(nil or 'ask-server) or gnus-read-active-file (nil, 'some or t) -
i still get the same startup behaviour.

i presume that i'm missing a number of things and /or doing a number
of things wrong . . . . ?

Any help would be much appreciated!

Alexis.