Well, I discovered that SOFTDEP using the GENERIC kernel config file
   actually works on my DEC 3000/300, but it doesn't work using my stripped
   down custom kernel config file.


huh.  my 3000/400 kernel is stripped down pretty bare. but i do notice that the
/300 model is not quite the same as the rest of the 3000 series -- there is one
config option for 3000_300 and one for 3000_500 (which covers 400->900)..


could you try removing things one at a time from the kernel to find out if there
is anything in particular causing this?