Matt, I would guess it's the DAC or driver, yes (although MC is not reporting DSD, but 176). I will email Michal too. He is currently in Iceland but accessing email.
Update: I moved to MC 17.0.183 and nothing changed re: DSD64. However, Mytek ASIO (USB) supports DSD128, but DoP doesn't, even working firewire. When attempting to do DoP DSD128 MC returns an error saying Wasapi-Event Style doesn't like 24/352.8k and it might be my device. EDIT: That makes "some" sense as the Mytek doesn't support PCM 24/352k for listening, but Michal posted on Mytek forum over on CA (June 6th) that "Mytek USB will be able to do 352.8k for the purpose of allowing 128xDSD"....so I'm not sure of anything right now, until I get regular DoP USB working here on Windows. It works fine on OSX, but not sure nay of those players yet support Dop DSD128.
By the way, this thread has a lot of "ASIO DoP doesn't work" which tells me that some education is needed. ASIO and DoP are two different protocols. They shouldn't (and can't ) be referenced together. ASIO is older and an offshoot of what Steinberg developed as a pro handshake. It does not require DSD to "ride" over PCM, but may end up being a lesser supported protocol for DSD, and is certainly not OS independent. IMHO it seems more development is going into DoP (DSD over PCM) as it takes advantage of the huge momentum in 24 bit USB computer audio, etc. and is available via OSX and Linux too, without driver manipulations. My $.02. But please, when you are reporting trouble with DSD make sure you differentiate ASIO and DoP and let the vendors know which one you are using.