What does "logged in" mean now?

Since the latest rebuild, the behavior of being logged in vs. not
logged in appears to be different. It used to be that IPB simply
set a cookie when you logged in, most likely the "pass_hash" one,
and optionally set a long expire time on it if you clicked "remember
me". Now, it doesn't seem to set any cookies like that at all, and
the status of being "logged in" keeps randomly changing back to being
logged *out* so I have to keep banging in another user/pass to get
to some features, to post stuff, etc.
.
Can someone please explain exactly how this is supposed to work?
This is *not* a browser issue, so please don't even go there. What
I'm asking should be clearly defined by Invision's documentation,
but I wouldn't even know where to look -- besides, it may be something
that's still not quite working right since the downtime and thus a
combination of things.
.
thanx; I really want to understand this.
.
_H*