Currently Being ModeratedFeb 10, 2013 2:46 PM (in response to Cfull)
Check your sleep settings in System Preferences/Energy Saver - make sure Computer & Display slider is not set to "never."
Currently Being ModeratedFeb 10, 2013 8:01 PM (in response to Cfull)Feb 10, 2013 2:13 PM
My macbook will no longer go to sleep either manually, by pressing sleep from the main menu, or on it's own when I close it.
Well it could be a bad magnet in the lid, or bad reed switch or loose connection to the logic board.
clamshell mode ? http://support.apple.com/kb/HT3131
If you can plug in external moniter to bypass- but hard to be definitive if you can not manually sleep from the .
You could do a safeboot to see if you have third party software interfering.
In terminal you can copy and paste to try and ascertain what is keeping it from sleeping:
pmset -g assertions
I would suggest a visit to the genius bar for more test.
Genius reservation http://www.apple.com/retail/geniusbar/
check warranty https://selfsolve.apple.com/agreementWarrantyDynamic.doMacBook Pro (15-inch Mid 2010), OS X Mountain Lion (10.8.2), 2.4GHz IntelCorei5 320GB HD 8GB RAM