The documentation says quite clearly not to hit OK, but to hit cancel.

At 12:32 PM -0500 11/6/02, Kevin Fisher wrote:
>Hi Folks:
>
>Just been playing around with Croquet.  For some reason when I start Croquet
>and hit "OK" on the URL it presents, I get a walkback.  If I hit cancel I
>can still play around though.  I'm at work behind a firewall so maybe that
>is affecting things.
>
>Anyway, this is all very stunning stuff!  I'm amazed at what the engine
>is capable of...that flapping American flag in that "maze" world looks
>very realistic.  The splooshing water effect is great!  I could spend
>hours clicking on Alan's face just to see it. :)
>
>Croquet immediately reminds me of an old VRML-ish 'environment' called
>Alphaworld.  Back in '95 it allowed people to connect with various
>avatars, moving around in a 3D world.  I don't know if they are
>still around or not..you could teleport between different areas in Alphaworld
>as well.  However alphaworld was very closed, and server based...and I
>gather Croquet is peer-to-peer.  Anyone remember Alphaworld?
>
>Anyway, Croquet is very cool...


--