I had problems before, but I now think it was the same one.


  It would be nice if we packed the directories more efficiently, and
  allowed them to grow beyond 256KB. But a lot of the cruft in this area
  is legacy to avoid breaking backwards compatibility with the way servers
  have been storing their directory information in RVM.

Well, that's unfortunate.  I wonder how hard it would be to make this
fail more gracefully, e.g. with ENOSPC instead of crashing.  It might
be worth having a server format change to remove the arbitrary limit
[ducking!]  (even though total RVM etc. is bounded, 4000 files in a
directory doesn't seem all that wierd...).