Recently I was testing a new workflow with a user in our quality environment. He claimed he wasn't getting SOME of the work items that were definitely assigned to him. I could see they were assigned to him in the workflow log. While I won't belabor the specifics of my investigation, I became highly suspicious that work items created on different application servers of the same SAP instance, were not visible beyond the server they were created on.
To test this theory, I assisted my user in changing his SAP login so that he was no longer logging in to the (load balanced) group server set up by our basis team, but to one of our two application servers. Once there we looked into the SAP Business Workplace (SBWP). Some of the work items assigned to this user were visible. We did this once more for the second application server. This time his inbox showed the remaining work items I knew to be assigned to him. In NEITHER case was he able to see ALL of the work items assigned to him.
ISSUED FIXED- I contacted our basis team and relayed our test efforts above. They DID FIX the issue, and now my user can see all the work items assigned to him. Upon querying the basis team as to what was causing this behavior, I received NO reply at all. 
They can be a rather proprietary group at times.
This issue looks very much like that discussed a couple years ago (http://scn.sap.com/thread/1122712). Unfortunately, there too, the solution was not shared.
Can anyone enlighten me? Kindest Regards to all and thanks in advance for your insights.