End of stream for op in Creative

Having this weird issue at the moment. There are two ops on my server, myself and another person.

Going into Creative seems to cause a problem for my other op. When she goes into Creative and tries to open the inventory, she gets an "End of stream" error (every time). It's fine when she is in Survival though. It doesn't happen to me at all, so we're not sure what's up or what it could be.

It doesn't seem to be her MC client/installation either, as we've tried it completely fresh and it still happened (besides that, our installations are almost identical).

Any ideas or suggestions as to what I should be looking for?

Running latest dev build, btw.