Macbook pro does not wake from sleep?

I have a 2010 Macbook pro with snow leopard 10.6.8. When i put my macbook to sleep, sometimes it will not wake up the next time i open the cover. I cannot do anything to wake the macbook pro and my only option is to hold the power button and force it to turn off and then restart the macbook pro. The front indicator light will be solid instead of flashing. Is there any way to fix the problem of not waking up from sleep?