E450 - hangs when booting without keyboard and monitor

I have an E450 and I would like to remove the keyboard and monitor.  I
powered the server down, and then removed the keyboard and monitor.  When I
power the server back on it hangs during the boot process.  If I power off
and reattach the monitor and keyboard it then boots fine.  I did not do a
lot of troubleshooting because I did not want the machine offline for a long
time, but was hoping someone might have a few tips before I try again.
 
I did have a console connection via my laptop to the serial port when
booting without the keyboard and monitor and did not see any errors.  It
would finish the memory initialization then start the boot process and just
hang shortly after that.
 
Regards,
Jason