Raw images appear overexposed in Lightroom

Hi all, 

I imported a bunch of photos into lightroom a couple of days ago and everything was displayed as normal, nothing out of the ordinary. Today I began editing them and noticed that all of my images are extremely overexposed, which they were not when i imported them and are not when i view them from my hard drive. Has anyone come across this issue before?? Please help!

On a side note, when i imported this album i 5 star rated the final ones and when i returned today, all the ratings were gone :'(