Tekkit Classic grey screen?

[theawesome624]

http://prntscr.com/a97nm6

Weird, but the first time I have been able to actually launch a modpack without it crashing immediatly

 

[billylathamxx]

Having the same issue!

I decided to open up the console and have a look and this it what it said;

Exception in thread "Minecraft main thread" java.lang.RuntimeException: sidedDelegate null when attempting to getMinecraftLogger, this is generally caused by you not installing FML properly, or installing some other mod that edits Minecraft.class on top of FML such as ModLoader, do not do this. Reinstall FML properly and try again.

It is really quite annoying.