You don't provide a ton of info here...what exactly have you tried? Any other hardware installed? Have you enabled the proper sleep states in the BIOS?
Knowing nothing else, my first suggestion would be to try the MCE Standby Tool. It's very simple to set up, and it will automatically configure your sleep states based on the criteria you give it.
Knowing nothing else, my first suggestion would be to try the MCE Standby Tool. It's very simple to set up, and it will automatically configure your sleep states based on the criteria you give it.