On the new 1.2 patch hardcore verteran difficulty entering the malmouth sewers from malmouth outskirts for the first time, the corridor leading from the zone in, to the wider area could not be navigated.
Cold not navigate past where the items in the screen shot dropped.
After killing all the enemies I was able to reach, and exiting the zone and re-entering. I was able to navigate again.
Maybe something to do with the worm type monsters that spawn in this area? There were many of these types as well as a hero imp that spawned in this chokepoint