I'm guessing John, or resident expert on these things, will want to see it, so please when it hangs, run Activity Monitor, select InDesign, and run Sample Process. You'll get a report. Upload it to http://pastebin.com/.
If it were an actual hang, he'd want you to do more, but we'll wait and see what he says.
Will do - but as Sod's law always applies in these circumstances, I'm now manipulating tables again, and InDesign is going through one of its periods of being good...
Yup, Peter is spot on.
This sort of thing can be tricky though...not quite slow enough to be easy to measure?
What kind of document is it? Hundreds of pages? Cross-references? Part of a book?
Have you tried exporting to IDML and re-opening? Does the slowness persist?