Bob, I'm running the same drivers as you now. No lock-ups or any other problems with the latest Fireface UFX drivers. Upgraded to USB driver 1.038 and hardware revision 353 and running smooth. Also using TotalMix 0.996.
 
Have you tried posting this on the RME forum? Matthias and others there are very helpful. Hope you get this resolved.

I'm running the UFX via USB with the latest drivers on X3D Producer on Win 7-64 and no issues as described by the OP. 
 
I did have this issue with an earlier RME UFX driver many moons ago.  In addition to the symptoms described above, I would also experience the issue whenever switching between ASIO applications - such as closing Sonar and opening BFD2 in standalone mode - the audio driver wouldn't be released when closing the first application, so the subsequent application wouldn't launch properly because it couldn't access the audio driver. 
 
Since you're already running the latest drivers, similarly as others on here who aren't having issues - I'd recommend reinstalling the drivers / firmware - or downgrading versions temporarily, then reinstalling the latest versions again.
 
Hope that helps.
Russ
 

Bob - do you by any chance have Acronis True Image on your system? I had a similar issue that was resolved once I uninstalled Acronis.

It is best to STOP acronis services when running your DAW. When you do a backup you can start them again.


The common Acronis shutdown issue was generally caused by:
http://kb.acronis.com/content/19016
 
This is a discussion about it:
http://forum.acronis.com/forum/44680
 
It should be a thing of the past (?).
If the OP has True Image they should also check for updates.
There is no need to remove Acronis True Image (if indeed this is the OP's issue) when you can just disable the services.
nb I run the 2014 version perfectly well.
 
Cheers...