The fact that the soundcard will not unlock is a clue. Something has the ASIO driver and is not letting go, it seems to me.

You should always be able to let the host contol the driver; part of ASIO design. Since you can't, maybe you need to check bit rates closely in RB or figure out WHY you can't unlock it.

16 or 24 bit?
44.1, 48, 88, or 96 kz rate?

They must match to work.
But still, since you can not unlock the driver something else appears to be interfering.
Maybe Cubase is locking it, or another program.. windows even!

and in my opinion it is not a very simple thing to ask a program to do; it's pretty demanding actually.

What is puzzling to me is that it works in BiaB and not RB.
The developers of the two work pretty closely together, there shouldn't be a major difference in how they work with VSTi, except that RB is a multiple driver DAW and BiaB is single driver.

I do not work here, but the benefits are still awesome
Make your sound your own!