Storport strange behavior

Hi I am facing a strange issue in storport miniport driver.

I wanted to map SRB data buffer address to system virtual address space. So I made Port configurations -> MapBuffers = True. Expecting databuffer will be mapped by storport and I can directly access SRB->Databuffer in my miniport. It works perfectly in Windows 7 Professional OS. But in Windows 7 Ultimate I am getting SRB-> Databuffer is NULL.

Is it an open issue in Microsoft. Or Is there any Hot fix available for Windows7 Ultimate.

Thanks and regards,
Muthu