This is driving us crazy: We have an OSX Snow Leopard installation with InDesign CS5.5 (7.5.2) and it hangs at random moments. On this Mac is also a single InDesign CS4 installation that's stable.
We have Suitcase Fusion 3 running, but when I sample the process when it's hanging, no sign of Suitcase can be found, so I think it's not the culprit. Otherwise there are no third party plugins I can think of. What we can say is that we can work relatively well at the beginning of the day (or after a restart), but after a while it begins to hang and after that it hangs more frequently every time we kill the process.