3rd stage boot loader can't find kernel after 'make installworld'

[thatcher hubbard]

  On an older Dell PowerEdge 1300, single 36GB hard disk connected through a PERC controller.  Installed from the 5.2.1-RELEASE ISO.  The machine installs fine, has no troubles getting at the disk through the 'amr' device.  I get CVSup on the machine, synch my source, do a 'make buildworld' with no problems and then a 'make installworld', also with no problems.  Upon reboot, the first and second stage loaders run fine, but I get a "can't find /boot/kernel/kernel" from the 3rd stage one.  Trying to do an 'ls' I get "open '/' failed: no such file or directory.
  I searched the mailing list and newsgroups and didn't find anything like this, and this is the second time it happened (tried re-installing the first time).  Is this something obvious that I'm missing?
  Thanks in advance to all.