I had this happen to me once...
Found I was missing 1 engine mount screw so when jumping my engine was moving ever so slightly but enought to hit my clutch bell on my spurr...
Also make sure your tranny is tight... If thats moves, even just a little it will do the same thing...
And obviously like said above... Check your mesh and dont over tighten you slipper..
Good luck.. let us know how you go