gnus suddenly slow searching active groups

[Michael Slass]

Hi:

I must have accidentally changed something recently, because now when
I go to check for new mail, gnus pegs the processor at 100% for about
a minute, while the minibuffer shows:

Reading active file from news.comcast.giganews.com via nntp...

If I hit C-g during that, I get a backtrace showing a buffer full of
group names.  I'm only subscribed to < 10 groups, and this behavior is
recent.

Any hints about what variable I might have changed (with an errant
keystroke in the Group buffer, perhaps) that might have caused this
behavior?

I'd be glad to provide any additonal info that might help

Gnus v5.10.6
GNU Emacs 21.3.1 i386-redhat-linux-gnu

Thanks.
-- 
Mike Slass