I would start at the top...go into BIOS, make sure you have selected S3 sleep and wake from keyboard AND wake from mouse are selected.
If that doesn't help, I would use Search at the top of the page for your motherboard sleep. Make sure there are no - signs in the name.
You can also look in MultiBeast under Drivers & Bootloaders/Miscellaneous for the appropriate kexts such as evOreboot.kext, but do some research before installing to make sure it is a solution for your board.