I have had similar problems for years on my Windows machine with a Saffire interface, especially with RAM-hungry sample-based VIs such as Spitfire's. My workaround is to do one of two things: wait 30 seconds or so and try again, or deactivate and reactivate the VI. I do the former if I need to get up for a moment anyway.
I have noticed that the problem becomes more frequent as the complexity of the orchestration increases. In other words, it seems to be related to load.
We're both using Firewire interfaces. Aging tech. Possibly a coincidence but...
