Stretch Bates

Hello All, Sorry in advance if this question has already been answer, I'm not sure what this would be called. Bascally, If i look up at the sky, In certain parts where there is cloud, The clouds have bits taken out of it in the shapes of like stars so to speak and also textures get messed up a little when I'm trying to build. I'm guessing this is caused by my graphics card because I had just recently got a new Computer. Any help would be appreciated :)