Dell Dimension 4600i with 1GB RAM. Installed Ubuntu 12.04 without difficulty. If left unattended, it appropriately goes to sleep and I can awaken it with a mouse gesture or keyboard press. However, if I use the Suspend command it sleeps and then will not awaken, forcing a hard reboot. Pretty new install. Not many modifications from the stock distribution. I am new to Linux and would appreciate any direction someone can give. Thanks.
Thanks to 2F4U on ubuntuforums.org, who got me pointed in the right direction. Google search for "how to install nvidia drivers in ubuntu" led me to
I tried System Settings > Additional Drivers but it seemed the "Nvidia accelerated graphics driver (version 173) [Recommended]" was already installed. I instead activated the "Nvidia accelerated graphics driver (post-release updates) (version 173-updates)". This didn't change the behavior. Still wouldn't recover from suspend.
So, lower in the above page is a Suspend/Hibernation section. I followed the advice to edit xorg.conf and blacklist.conf and now I can recover from suspend.