Major clutch mishap!! Need InstyHelp!!!!

[bronson@inwave.com (Nate Mellom)]

This is on the '84, 1.8 JH, 4K.
I was pulling to a stop sign, and I pushed the clutch in to downshift. 
 It went about 1/4 of the way down, and them POP!  There was a 
semi-loud, semi-metallic popping noise and the clutch pedal went 
straight to the floor.  I put it in neutral, let the pedal up, it came 
up good.  Pushed down, there is NO resistance.  My first thought was a 
broken clutch cable, but I checked under the hood and the cable is fine, 
the clutch actuator lever works and everything.  I can pull the lever up 
by hand.  There were no symptoms, it just popped.  Some background:  I 
did do a motor swap in February, and I re-used all the existing clutch 
parts (it was a recent clutch to begin with).  When I re-installed the 
clutch I followed Bentley to the letter.  I've never had any problems 
prior to this.  I do have a slow tranny leak, but I don't know if low 
fluid would cause an instant failure of whatever failed.  I had to get 
it home, so I put it in first and started it, and idled home (5 blocks 
or so).  It would pull out of first, and I tried to get it into second 
for fun (sans clutch), but there was nothing, it didn't even grind, and 
never went into gear.  Tranny shifts fine when the car is off.

As of now I'm assuming I'll be pulling the tranny soon, but I'm at loss 
as to what could have happened.

HELP!!!!

Nate