The stripes are running perpendicular to the film edge, not down the length of the film strip. Because of that, I ruled out anything happening post-development, and think it must've happened either in the tank, or, conceivably, as mentioned, in camera. I'll shoot another roll under the same conditions and see if it happens again. If it does, I'll probably have to take the camera in for a check-up.
I loaded the film in my darkroom, which I've tested thoroughly for light leaks -- found none. It is carpeted, though, so I guess static is a possibility. I didn't see anything that would've alarmed me while loading the film, though. Ah, the mysteries of ESD.
I'll definitely try re-fixing and see if that helps. Couldn't hurt!
Love all the help I'm getting here. I greatly appreciate it! You're a very supportive (and knowledgeable) bunch.
Off to try the fixer rescue....