Error in Process in PO for Classic Scenario

Hi,

I am working with classic scenario. I have created one catalog for services where I used service as a catagory(from backend R/3).

I have maintained contracts for this services in the Backend R/3 as well as vendor lists with respective contract in SRM.

I have maintained sourcing never carried out as I want direct PO in R/3.

But when I shop this services from catalog I am getting one error like Error in Process .

I can check this status in followon document tab in Shop.

So how to move for this error...Kindly suggest.

Regards,

Navneet