Hi,
I know your problem. We are a couple of MX-freaks who ride different models of Husabergs.
A friend of mine bought a new bike last year (also a ´03 model). He had also noise coming out of the clutch side. First of all we had to change the nut on the driving shaft. It was the wrong part for this enginge. The result of the wrong nut was that the gear wheel on the driving shaft was getting loose after riding a longer time with higher rpm´s (hot engine).
Half a year later we found out that the driving chain was very very loose and scratched the crankcase. The camchain tensioner was in the end-position, but it could not be that the chain has to be replaced after 20h using the bike. So we heard from our dealer that there is a new designed camchain tensioner (the plastic thing that´s pressed against the chain). With this part the chain gets more tension.
Did you have some metal bits in your oil screen? That would be a hint if the chain is scratching the crankcase.