I have a 2011 15'' macbook pro, and its been acting strange lately. About 30 min ago my macbook froze when i tried to open iphoto. i then proceeded to hold down the power button in order to restart it. when it turned it back on the screen came up that prompted me to type in my password and it was totally different than normal, it was the lock screen for os x lion... im using snow leopard and have never had lion installed. so i entered my password and everything else was normal. Also recently whenever i restart my mac (completely power it off then on again) it does something funny like this. for example sometimes my wallpaper will change to something i had previously used. Or i will have to reinstall a program called "SafeConnectMacInstaller" that i have to have in order to use my universities internet (actually it makes me reinstall this every time). If anyone has any ideas about what might be causing these problems, it would be GREATLY appreciated. Thanks. Another thing that might be worth mentioning is, sometimes when im watching netflix my screen will freeze into the "blue screen of death." when this happens i have to completely restart my computer. when i looked up what might be causing this problem i read it was probably due to heat. but im not too sure about that because when i play games it gets pretty hot too but never freezes.