The old link should be the same, since we redirect to the new forum, but just in case your link is still redirecting you to the old - non existent forum, try inserting http://www.plasticscm.net and update your bookmark.
Users + password have been migrated, but with the new system, generating "requesting" a new password is a 1 minute job, fully automated.
We hope you enjoy the new forum as we do, and feel free to share your ideas there with the Plastic SCM growing community.
regards,
miller
