Yeah, it is intermittent. I don't know that I've been able to peg it to any particular collections. I'm currently unable to reproduce the error, but when it happens, it just doesn't let up.
Several times, I've tried on a different computer an hour or so later and everything's back to normal, so I don't know if it's an issue with my older desktop (that's where I've run into it before) or some other time-dependent factor that would reproduce itself on other machines.
Next time I see this behavior, I'll try to test on multiple machines at the same time and report back.