It seems so, as my opponent has managed to do it twice now in this game:

http://www.youplay.it/beta/play/ws_GameMove.asp?GameID=5574

In the first instance, the London was alredy fouled with the the Provence, and when the Provence sank, the London remained fouled. Finally, several turns later, the London unfouled itself. In some ways, this fouling makes sense--a ship that is sinking is not going to unfoul itself just because it is sinking. Whether floating or sinking, the Provence would still act as an anchor to prevent the London from moving. As unfortunate as it was for my opponent, I like the realism of this fouling.

In the second instance, however, the Royal Oak made the mistake of drifting too close to the hex where the Duc had been sunk. I don't entirely agree with the new rule that a ship can't pass through the hex where a sunken ship is located--how deep is this water again?--but it makes even less sense that the Royal Oak managed to foul its rigging with the sunken Duc. In cases like this, I want to say that a ship can't foul its rigging if the other ship is already sunk, and my opponents complaints are fair.

That being said, it was a lot of fun raking these two ships repeatedly while they have been stuck! (Just glad I wasn't on the receiving end.)