Weird, when Cubase is open and I open Microsoft Word or Excel (which has some notes on my music projects) the Office document freezes. It ONLY happens when a specific Cubase project is open. When I close the specific project, with Cubase still running, the Office doc responds instantly.
Any ideas on where the conflict is??
Yes I do have an idea where the conflict is. But I am going to make you read a bit of a rant first, so that you will better understand the problem.
TLDR: …Studio Setup and see if you have the checkbox ticked that releases the driver when Cubase is in the background. Tick that, and then to be sure, close down Cubase normally, and reboot windows and see if you still have the same issue. It might work 
The Microsoft office team at one point about 20 years ago had done just about everything anyone really needed for the suite of products they provided. Most anyone who worked on the team was long since vested and had gone off to a startup, or to do something more interesting. Those that were left needed something to justify their existence, and the Dot Com crash had just happened, so they started integrating every smidgen of the Windows OS into their product, to enable features that no one needed or asked for, or have even considered using since. ( Simultaneously they gave the UI an overhaul intentionally contradicting every bit of research into human computer interfaces. If this wasn’t enough, they also had the mandate to keep new versions backwards compatible with older files. ) 
In the midst of this chaos they threaded every “service” or OS integration though to the whole application, ignoring multi threading standards that any freshman computer science student could immediately spot as problematic.
Therefor, if there is any kernel level computation that conflicts with that “We are MS, we own the whole device” philosophy, the application freezes. Even when that conflict has nothing at all to do with what you are using the MSO application for at that time.
With this knowledge, A first guess is that Word or Expel has sent some message off to the audio driver. I know this sounds ridiculous which is why I groused about how ridiculous it is before mentioning it.
I don’t know that this is the case, I am only guessing, and I can’t test it as I do not have MSO on any device.
I don’t even know if the suggestion I am about to make would have any effect on resolving the issue, even if I am guessing correctly. I also can not validate that this guess is correct if the possible solution happens to work. I don’t have MSO installed anywhere. I know I already mentioned that, but I thought it was so important that it was worth mentioning twice. 
That said, go to Studio Setup and see if you have the checkbox ticked that releases the driver when Cubase is in the background. Tick that, and then to be sure, close down Cubase normally, and reboot windows and see if you still have the same issue.
It might work
Great info. That makes sense. I’ll try to disable the setting to see if it works.