I have downloaded the latest USB and FireWire drivers from Behringer's website, and it makes no difference whether I use it on Windows 7 or 10, on FireWire or USB.
I have contacted Behringer's UK support people, who initially appeared concerned and helpful, but haven't been. I have sent them HW activity logs and screenshots of error messages. Anyone else who wants to see these can look here: https://www.dropbox.com/s/5nrf82ctwiqfr ... s.doc?dl=0.
Having worked with Hauptwerk for nearly 12 years now, using a range of other interfaces including M-Audio Audiophile 2496, Delta 1010LT, Profire 610 and FastTrack C600, Focusrite Saffire LE and Saffire Pro 24, and MOTU Ultralite Hybrid Mk3, I have never encountered this problem on any interface other than the FCA610.
We need to get Behringer to fix this, as it is obviously a Behringer problem and not a Hauptwerk one.
Can anyone in the US/Canada put me in touch with support people over there? I find they are usually much more helpful than European-based ones. Names & phone numbers would be even better.

Additionally I would suggest that anyone else experiencing the same problem should e-mail Patrick Karvounis (Senior Specialist, Care) on carecrea@music-group.com quoting
Support Request (Case: 00596829) [ ref:_00D2818RET._50028m0Mo6:ref ].
Thanks in advance for your help.