[plt-scheme] Module instantiations for servlets

I have two servlets, a.ss and b.ss, that share a module util.ss with
some state.  The web-server seems to instantiate util.ss twice (once
for a.ss and another for b.ss) so the data isn't shared.  Is this a
bug?

If it's not a bug, how should different modules of a web app share
state?  I'm splitting the website into different servlets so it's
possible to link to different sections (e.g., a user profile) instead
of always to the start.

Daniel