snapshot dump hangs

[Randy Bush]

i try to dump a live filesys with

   /sbin/rdump 0Luaf remote.sys:/backup/foo/var.dump  /dev/twed0s1d

the screen does

  DUMP: Connection to remote.sys established.
  DUMP: Date of this level 0 dump: Wed Jun  9 01:52:32 2004
  DUMP: Date of last level 0 dump: the epoch
  DUMP: Dumping snapshot of /dev/twed0s1d (/var) to /backup/foo/var.dump on host remote.sys
  DUMP: mapping (Pass I) [regular files]
  DUMP: mapping (Pass II) [directories]
  DUMP: estimated 513616 tape blocks.
  DUMP: dumping (Pass III) [directories]
  DUMP: dumping (Pass IV) [regular files]

and then just hangs forever

there is nothing in /var/.snap

i can

    mount -u -o snapshot /var/.snap/snap1 /var

this is horrifyingly reproducable and happens with other source
filesystems.

any clues?

randy