Tekkit won't load but everything else will?

[xXPartyPoisonXx]

Okay so my when i try to load my tekkit it gets to the mojang screen and then gives me an error report that goes away to quickly to read and then it's just a white screen! Technic, yogbox and vanilla all work but tekkit just wont load. What have i done wrong? It used to work!

[Cereal Guy]

I have a similar problem but I dont get the error screen, I get the background you get when you are on the multiplayer screen (the dirt texture) then the white screen