Singapore Airlines KrisFlyer - booking a Y seat on a VS points award

Hi experts, did a search and can't find an answer to this. Mr pschafer are in the process of booking an SQ award SYD-SIN-CPH (return) using VS points. We had it all locked in, in business class but due to some sort of "issue" on the part of VS or SQ the tickets were cancelled - no one can tell us why. When trying to recover this situation, VS now tell us that the SYD-SIN leg no longer has award availability on the 773 flight but have offered us Y on the 380 flight.

So here's my question - if we accept this (rather than look for alternate date - which is possible as this trip is Aug/Sept 2010) can we pre-book seats in Y (I know you can in C)

Thanks for any help on this.