Mojang screen off centre and tekkit crashes?

[Mr-nick]

Hi guys. Ive been happily playing tekkit classic for the past few weeks with no issues, but now when I try to load up any of the modpacks from the technic launcher they get as far as the mojang screen...but I can only see the top right hand corner of the word 'mojang' down the bottom left of my window? If it doesnt completely freeze here (which 9 out of 10 times it does) then it will enter the Minecraft start screen (with single player etc tabs) but once again only the top right part of it is visable from the bottom left of the window...then crashes!

Ive tried removing the entire technic folder from my application support folder and re ran the tekkitlauncher.jar file from fresh...but its still the same.Im using a macbook that is pretty old but once again I had no issues whatsoever a few days ago.

Any help will be would be ossum.

Cheers