supplied unit of measure and the primary unit of measure issue.

Hi,I am creating an internal dropship order and as part of that I am running the intercompany AR invoice program in Inventory and it has generated an interface line in autoinvoice interface. However it is not going further from there when I run the Autoinvoice. I get the below error message. 

"The supplied unit of measure and the primary unit of measure of your system item must share the same unit of measure class"

I checked the document id 1132807.1 mentioned on Oracle support and can see that there is no discrepancy in the unit of measure definition for both the operating units. I also checked the item conversion setup in Inventory. Since I am not expecting any conversion I dont see any record of this item in intra and interclass tabs,which I think is ok.