Error code 06 011 on shopping carts

Hello,

We are on SRM server 550 and recently upgrde to stack SAPKIBKT15. All the created shopping carts run in error with the following error message:

Shopping cart 0010002781 (PReq. 4000000523): 06 011 Item 00020 does not exist (Document Number 10002781

Can any one help me on this one ?

Thanks as ever!