Hope someone can help me with this unusual problem. I installed Ubuntu 12.04 server on a Gigabyte GA-H61M-USB3 motherboard. This all went well. I subsequently installed Apache, MySQL and PHP. This also went well. I am using the UFW kernal firewall instead of the recommended Shorewall (could not find the repository during installation). I thought I had a working server until I relocated the box and attempted to log in using PuTTY. Turns out that the server does not boot without a monitor and keyboard connected. I don't believe there is anything in the motherboard that is preventing the boot. Has anyone else seen this behavior and what was your fix. Thanks.
Have you verified that the system does not boot? For example add something like
to /etc/rc.local and check that file after reboot.
Are you using the correct IP to connect via Putty (static vs dhcp configuration)?