Occasionally, my MacBook Pro (13-inch, Mid 2010) won't go to sleep when I close it. When I close the lid, the fans keep going and the computer slowly becomes warmer and warmer, louder and louder. Also, when the lid is closed, the little white "sleep light" on the front of the computer ignites solid (does not pulsate, as it normally should do when asleep).
Then, when I open it back up, the screen will not turn on (it remains black), the white "sleep light" turns off (still no pulsating) and the computer becomes completely unresponsive to any kind of keyboard, mouse or trackpad input. It simply won't respond to anything.
When this happens, the only "fix" I've found so far is to hold down the power button until the machine turns off completely, and reboot. At which point it seems to be working fine again for a while. This doesn't happen every time I close it; only occasionally.
It almost seems like sleep mode has been "inverted" in a way. I'm not even sure if this is likely to be software or hardware related issue, but it started happening after having used OS X Mavericks for a while, and has persisted after upgrading to OS X Yosemite.
I saw a couple of other similar questions and answers, but nothing that quite seemed to match the description above, and I haven't been able to find a solution for my problem in the other questions. Has anyone seen something like this before?
Any help or pointers greatly appreciated.