@Stuart – can you tell us more?
I'd try a Save As with the document giving the document a new name and proceding from that. Before doing anything new, restart your computer.
What OS? How much free space on the system disk?
Once I get the message it goes into an infinite loop and the only way out is to force quit.
OS 10.9.3, 600gb of HD space and 14gb of RAM, no other apps running either.
I'll try recreating the document and seeing if I suffer the same problems. It may be something inherently screwed with the file. Thanks for your reply.