So here's an interesting one. While playing through Chapter 4, I'm now stuck in the holding cell with LeChuck after Guybrush's charges were dropped. I can still have conversations with both LeChuck and The Voodoo Lady, and Guybrush will show up outside the cell when I end them. But as soon as I start to move I'm shunted back to the cell.
Here's a screenshot.
2012-09-10_00001 by bluepotatosack, on Flickr
Any idea how that happened? When it happened I clicked on the reinforced wall before TVL grabbed my attention.