Seriously? After several days not even an acknowledge for the case posted? Never mind. After reading the a thread called "CyAPI.NET bug" on this very same forum (http://www.cypress.com/?app=forum&id=167&rID=42392), I found a similar description for the problem I've encountered and actually the lead for solving the problem. It gets solved once you pin the three byte buffers in memory (Overlapped, SingleXfer, and the data buffer) used by the async transfer methods.
We experience similar problems with asynchronous transfers.
Since the way of cyusbs asynchronous transfer does not really comply with c# standards, we use the cyusb asynchronous wrapper provided by [http://www.virtualroadside.com/blog/index.php/2007/12/08/psoc-usb-suiteusb-net-cyusb-asynchronous-wrapper/] which works fairly nice for a small amount of queued transfers (<10). If we queue more transfers the application fails.
You mentioned that you got things working. Would you be willing to share your solution (code)?
Thank you very much.