So, I'm co-writing a Googledoc with another Board member. It's been working fine for the past few weeks, but now when I open it it comes up with a message telling me about a "server error" and asking me to reload. Reloading doesn't help, so I tried X-ing the box. The document then loads for a couple of pages, then the same message comes up again and when I X that one the document refuses to load any further.

Any idea what's causing this or how I can stop it?