Migration error after upgrading project to Rails 2.0

Hi,

I started writing a project using Rails 1.x, then moved to 2.0 a
couple of weeks after it came out. This moved the project to the new
migration structure (timestamp based), and everything's worked fine on
my development environment. I've since done the initial deployment of
the project to my production environment and the initial DB migration
ran fine and the application works as expected. A couple of days ago I
created another migration and it worked fine on my dev environment,
but in the production environment it comes back with the error:

rake aborted!
PGError: ERROR: relation "schema_migrations" already exists
: CREATE TABLE "schema_migrations" ("version" character varying(255)
NOT NULL)

It seems to think that it needs to switch the project over to the new
migration tables again. Has anyone come across this before and have
any ideas how to fix it?

Thanks,
Simon