clay mode works but not basic Vray materials

Hi,
just purchased SR today and got a nice clay fly through animation working, only problem is when I use the proper scene materials the LC just hangs its calculation on about 90% and never progresses beyond that. it progress at a steady rate then stops progressing.
I have stripped my vary materials down to very basic to see what is causing the problem,

Can i calculate LC and IR with clay mode and then flip over to my vray mats for sequence3?
thanks
T

hey Jérôme, seems to be working now, maybe some buggy geometry, I am not sure, tried so many things- cant recall which one fixed, fingers crossed, will see what the morning brings,
cheers

UPDATE:
working like a threat now I think there was some dodgy material that was screwing things up,
did a test and nice and smooth, no flickering, rendering times are good, lloks like this week wasn't a complete write off