No printing happening in VF31

D Friends,

I'm trying to give bulk printing of Invoices from VF31. But no printing is happening. I'm getting following errors:

With Processing mode 1- No messages for initial processing exist. Message no. VN108.

With Processing mode 2- No messages for repeat processing exist. Message no. VN109.

I've searched the forum- got many hits on the same message no. like : "http://scn.sap.com/thread/1887696". But they are not solving my issue. Do I've to run bulk billing from Spool (SP01) or bulk printing will happen directly from VF31?

Thank you.