I was having the same problem even after updating everything. The PC would go to sleep, then I would press the space bar to wake up the computer and the computer would wake up, but the mouse and display would not wake up. Strange. After playing with this, I discovered that if I clicked the mouse first and not the keyboard everything would wake up properly. The keyboard is a PS/2 connection and the mouse USB. That the keyboard was PS/2 seemed to cause a problem on my PC because I connected a USB keyboard and everything is waking up now.
Windows 7 32bit
EVGA 122-M2-NF59-TR Socket AM2 NVIDIA nForce 590 - Motherboard
Video Card -- Gigabyte GV-NX73T256P-RH NVIDIA GeForce 7300 GT Video Card