BBenve,
Your problem is not all that foriegn to me, though it is a little different.
The same thing happened on my sisters 333mhz iMac (strawberry, I think). I had just gone through and cleaned her system, found a massive virus and decided it was best to start from scratch (saving what files I could to a CD). Well, everything went good in the installation but after the restart we encountered your problem.
What I am going to tell you is going to conflict badly with everything you have ever been taught about computers. What we experienced was a once in a million, though it may give you some sad insight.
We got to login screen (actually this was under OS 9) and typed in the password. At that point the machine pretty much went dead. We restarted and got the same results the 2nd and 3rd times. Boot from CD? Nope. PRAM? Nope. No Extensions? Nope. We were stuck and a little fustrated. Called the Apple rep, and managed to stump him as well (including three other reps).
Finally, we sent it in for repair and got a call a couple of days later from an Apple tech telling us that part of the motherboard had been fried somehow. He suggested a power surge. I aksed him how I was able to at least get to the login screen. He had no answer to that. From my understanding, this is a case that has never happened before. You should look into this as a possibility, albiet a sad one.
Best of luck to you.
Magnolia1240
