Sometimes, the BIOS has options for how to handle power buttons, lid open/close, etc. If it's never booted Ubuntu before, it would be useful to look over the BIOS settings.
Does the power LED indicator show it went into suspend? If not, then the suspend process never completed. This is likely to be a peripheral without suspend support.
When the lid is opened, does the power led still indicate suspend or does it indicate that it's running and trying to resume? If the former, then the lid open signal was never received and this could be a BIOS or hardware issue. If the later, try to ssh into the machine from another to see if you can tell what's going on. Thia may not work of resume didn't get far enough. Killing the X server will start a new login session and do a full reset of the graphics if it's the graphics that's hung up. You can also try to pull up a terminal with ctrl-alt-fN and then return to the GUI which might bring it back.
If it looks like it started to resume and you close the lid again, does the LED go back into suspend? If this is the case, ssh should work when the lid is up and that would be the best way to see what's happening.
You should also look at /var/log/kern.log to see how far it got if it started to resume, but couldn't finish or if it failed to completely suspend. This could help narrow down the problem. It generates quite a bit of noise when suspending and resuming.
If it fails to boot, wait a few minutes before power cycling so that anything waiting on timeouts might leave a log trace. There could also be something slowing down the resume by waiting on a timeout, so try waiting 10 minutes or so before giving up on the resume and if it does resume, the logs should point you in the right direction.