I have the exact same problem. Worked fine in vray 2 in the same file. Cant figgure it out. Using the material wrapper. Going back to 2 just to render this out.
Hopefully we get an answer from somebody because most of my images are all on a pure white background and I need the Matte properties to work correctly.
Yes, it is fixed now for the next nightlies tomorrow; if the tests are ok, the fixes will go into the stable builds sometime later in the week. Access to the stable builds you can get if you send an email to support@chaosgroup.com