Can't get BackgroundRb to work

I’m trying to get BackgroundRb to work. I’m runing on OSX 10.4.
My install went ok but strangely this command didn’t work

script/backgroundrb/start -p 11111 -d

I get the error

start: invalid option: -p

So instead i’ve left out the -p 11111

script/backgroundrb/start -d

which seems ok but when my controller calls my worker I get

undefined method ‘start process’ for nil:NilClass