Jon,
Look back in the archives to last July-August. There was an entire thread on the subject. Essentially, the Eureka needs a mandatory inspection and even though it should have still had enough time to run at Railfest 2005 before the time expired, the "officials" said otherwise!
I haven't heard whether Eureka was able to get an exemption or not or what the final disposition of this entire affair is. It's entirely possible that nothing has happened as of yet. I'm sure that Dan will let us know if and when Eureka is allowed to run again!