"But about a minute later it goes back to being unaccessible."
That's weird, VERY weird...
Well, try to disable any remote access to your router administration (just to avoid someone remotely messing up your router settings), then try to re-setup the later settings.
In the last case, try to install a new firmware to your router.
Hope it works for you.
Last edited by sparc86; 07-21-2008 at 01:54 AM.