I have recently installed Ubuntu 12.04 on a Hp Pavillion and whenever I enter suspend mode, my session is not resumed.All I get is a black screen.I have looked up other answers but they don't work.
You can try this - http://ubuntuforums.org/showthread.php?t=1978290
It might work :)
Same issue here but with 13.10 64bit, however the problem for me was the Nouveau display driver.
I am using Nvidia, and moved to a proprietary Nvidia driver, rebooted and suspend now works fine.
So I would suggest checking what driver you are using and changing to the proprietary driver available for your system.
Check in: SYSTEM SETTINGS / SOFTWARE & UPDATES / ADDITIONAL DRIVERS