Have you tried using the American Audio ASIO driver rather than ASIO4ALL.
I know my controller (Hercules 4-Mx) doesn't work with ASIO4ALL maybe your VSM4.1 doesn't too.
I would try the AA ASIO driver (if you haven't already

)
I've just done a quick google and found this
http://www.vms4dj.com/downloads_uk.htmlI think the latest driver is v1.2 (VSM 4 and 4.1 use the same ASIO driver)