I am no "guru" on the SAP adapter but I am aware that there are potentially some limitations getting data out of BW cubes. How well does it work getting data from core SAP tables for you? My experience is that the core tables work very well with the core adapter.
Also, are you sure that you are using the "QvSAPConnector" to get the data from BW? I thought that one of the other 3 SAP adapters was used for BW.