Can't update? Cant play, either?

[AeroForceOne]

After using the Attack of the B-Team modpack for a few days, it asked me to update, I clicked yes, but it came up with an error saying it couldn't delete chicken code (essentially) 

 

I figured I wouldn't update it. now every time I try and play without updating, it loads the files, then NOTHING. No windows open, no windows close, nothing.

 

[Munaus]

Please post in Bug Report and remember to add the error logs