MacBook Pro screen turns black when I open my laptop

hey everyone,

on last couple weeks, screen on macbook pro (purchased july 2011) has started turning black/going sleep whenever open laptop. problem can fixed if press 1 of brightness keys (sometimes) or unplugging laptop. indeed, problem ever occurs when laptop plugged in (it works fine when not). know how can fix this? laptop still turns on , still see log-in screen couple seconds before goes black.

thanks!

 

i have exact same problem 17" mid 2011 macbook pro. have taken apple store, , cannot find problem, have told me backup, , reinstall applications individually, believe it"s 3rd party software issue somewhere........frustrating!

 

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