Problem with Macbook Not Waking from Sleep

Recently, when I have been putting my macbook to sleep, it dosent go to sleep completely. Instead, the display goes to sleep (indicated by white light turning on and staying "solid"). The only way I can get it to come out of this stage is to do a hard restart.

When I turn it back on, the I see a gray screen for a few seconds, then it goes black (and the white light comes on), and then it appears to initiate a second restart again and boots all the way.

It appears to happen more when I just close the lid (with out going to Apple-->Sleep), but sometimes it does it when I go put it to sleep through the menu as well.

How do I resolve this sudden problem that is starting to get annoying, and is surely not good for the computer itself.

BTW, I searched for this problem on both Google an in the forums, and found sine similar instances that date back a while ago, but it seemed that everyone suggested to install the newest software and/or firmware (I cant remember which one) and it was supposed to resolve it.

I have also tried repairing permissions and restarting PRAM, neither seemed to help at all.