I recently upgraded from VV2.0 to 3.0 (run on Win2000).  When using my old Edirol UA-5 USB interface, no problems (aside from the USB bus choking out on large projects).  
But now that I switched to a Terratec PCI device (ASIO, the latest Win2K drivers) projects play fine in 2.0, but when playing the same projects in 3.0 I get "The request is not enabled for this device." and there is no playback at all.  I don't have a clue what this means.  How do you 'enable a request'?  Any ideas?