Got any network drives mapped to servers which are unreachable?
Are any other programs non-responsive? Programs which stop responding to messages from Windows can other programs to freeze while they wait for broadcast messages to timeout.
Both of those things can cause odd freezes (not just in Opus) which aren't obviously related to the action you're doing at the time.
If it's not those two then I'd recommend working down the General slowdown or instability investigation steps list.