This happens quite often to me and it is reproducable here. It happens when I open certain source files in a relatively large svn checkout of the boost project. After closing the text editor (it doesn't matter which one I use) Thunar just hangs, i.e. it does not redraw its window contents anymore and it does not react to any userinput (say pressing CTRL+W to close it). Thunar 0.9.3 on an XFS partition
I forgot to mention that this is a result of the fam daemon hanging, after killing famd thunar is back to normal again, except for the missing fam functionality. If I start famd in verbose debug mode the lockup does not occur anymore (probably things are slowed down by lots of messages to the console and thus the race condition doesn't manifest).
There was indeed a possible hang in the fam backend, but that has been fixed in trunk. So please try the next release of thunar (0.9.93) which will be out soon or compile from svn.
Please reopen if this is still an issue with the latest Thunar release.