Hello Vault Hunters!
It’s come to our attention that some users may be unable to progress past the “Pass through the breach” objective of the “The Beginning of the End” during their second playthrough. Our engineers have prepared a hot-fix for this issue which will be applied to your game at the "press start" screen as long as you're connected to the internet.
To discuss this with other members of the Borderlands community, please check out these threads on the official Gearbox forums:
PC: http://forums.gearboxsoftware.com/showthread.php?t=387016
PS3: http://forums.gearboxsoftware.com/showthread.php?t=387016