Hi guys, sorry in advance if this has previously been covered, i did do a quick search of this sub-group but couldn't find anything. My Mid-2012 13" Macbook Air freezes intermittently whilst playing Youtube videos. Literally it'll be a case of it freezing when i press play, or at some point during the video the picture and sound might stop, or the picture will stop and the sound might keep playing. Sometimes i am able to move the cursor, other times i'm unable to do so. I know its crashed because i have set the colon in between the time (e.g. 18:19) to flash in the taskbar. I've updated adobe flash player to the latest version and what not. I use firefox has my browser. Ive reset the PRAM via booting it into safe mode and then restarting, however it did get stuck on a blank grey screen, so i had to hold down the power button to turn it off and then on, and i was then greeted with a message saying it didnt shut down properly. I just don't know whats causing all this stuff, would a fresh installation of mavericks help? I hope you can help me out, thanks.