I had the same thing happen recently.  First time though.  Wouldn't connect to the network at the time, either. I THINK what happened is my ferret pulled the plug out of my router because I wasn't giving her enough attention (not exaderating, she actually does that).  I open the browser and it defaults to offline mode.  Since Windows is a big, veiny intertwined machine something wondrous and magical happens and other things get all screwy because it is working offline.  I open Poser and the library doesn't work because  of aforementioned magic.  I plug the router back in, deselect "work offline", and now everything works fine.

I don't know whether or not this is accurate, but worth a shot. Makes sense to me though because of the above posts on internal TCP connections, but I try not to figure out how Windows does that stuff because when I do it usually leads to a lot of swearing and a total system reinstall.