Can't reboot from ssh command line

[Craig Hagerman]

HI,
I have experience with other Linux distros, especially Debian, but
this is my first time with Ubuntu. I installed Hoary Hedgehog AMD64
onto a computer I will use as a headless file server. I did apt-get
update and some other installs, but it is mostly a vanilla install
right now.

The problem is that I access the machine via ssh, and for some reason
it will not reboot via the command line from another machine. That is,
if I enter:
shutdown -r now
from the remote machine, it gives the message that the server is going
down.... I am disconnected ... but then it doesn't come up. (I have
checked and it DOES continue to run - I wonder if something is
hanging?) If I do:
shutdown -h now
it shuts down OK. 

Also (strangely enough), if the machine is connected to a monitor (and
I am logged into gdm) and I enter "shutdown -r now" from the local
terminal it WILL restart without any problems.

This is driving me crazy. To make matters worse, this machine is on
the other side of the world from where I live (where I will administer
it via ssh)... and I go back home on Tuesday.

I would really appreciate any help or advice to figure out how to fix
this problem. On a related note... is there any way I can have the
machine shutdown and then turn itself on and some later time?

Craig