This article will explain which areas of BugNET are affected by lost machine keys, and how to rebuild a BugNET system without it. In the end you should have a fully fledgedsystem under control of "admin" and will then need to reset the users passwords to allow them to login.
I present two techniques, one will require some minor code to be written, and the other some SQL scripting. I have used the SQL technique on a hosted box with success....