Make sure you use NVDA with a braille display.

STR:

1. Download 1Password 6 for Windows Desktop from here. Choose the Download link on the same line as the top-most version number.
2. After installing, sign into an 1Password account. The problem will most likely show in this password field already. If you don't have an 1Password account, just create a new vault. Anything that triggers a password field should suffice.
3. After hitting the first letter in such a password field, NVDA will freeze. An error sound will play, and literally nothing is possible after that because NVDA will remain frozen even if the 1Password window is closed. The only thing that will make it wake up again is by shutting down Windows. The moment the desktop goes away and Windows restarts regularly, NVDA will return and close down normally.

When this freeze happens, the following is recorded in NVDA's log file:

AttributeError: 'NoneType' object has no attribute 'rindex'
ERROR - eventHandler.executeEvent (16:27:01):
error executing event: caret on <NVDAObjects.Dynamic_EditableTextWithoutAutoSelectDetectionUIA object at 0x05148E90> with extra args of {}
Traceback (most recent call last):
File "eventHandler.pyc", line 143, in executeEvent
File "eventHandler.pyc", line 91, in init
File "eventHandler.pyc", line 98, in next
File "NVDAObjects__init__.pyc", line 925, in event_caret
File "review.pyc", line 167, in handleCaretMove
File "NVDAObjects__init__.pyc", line 958, in makeTextInfo
File "NVDAObjects\UIA__init__.pyc", line 125, in init
COMError: (-2146233079, None, (None, None, None, 0, None))
WARNING - watchdog.watcher (16:27:26):
Core frozen in stack:
File "nvda.pyw", line 191, in
File "core.pyc", line 385, in main
File "wx_core.pyc", line 8657, in MainLoop
File "wx_core.pyc", line 7952, in MainLoop
File "core.pyc", line 358, in Notify
File "braille.pyc", line 1809, in pumpAll
File "braille.pyc", line 1672, in handlePendingCaretUpdate
File "braille.pyc", line 1678, in doCursorMove
File "braille.pyc", line 970, in update
File "braille.pyc", line 849, in addTextWithFields
File "NVDAObjects\UIA__init.pyc", line 445, in getTextWithFields
File "NVDAObjects\UIA__init_.pyc", line 432, in getTextWithFieldsForUIARange
File "NVDAObjects\UIA__init_.pyc", line 271, in _getTextWithFields_text
File "UIAUtils.pyc", line 117, in iterUIARangeByUnit

NVDA version next-13634,57644bf9

Narrator can handle these password fields without problems. Haven't tried NVDA without braille, though.