My guess is that this isn't a bug, but when you applied the patch, it didn't take immidiate effect. In other words: the patch copies a few updated files into your BD directory, but doesn't interfere with your savegames.
When you got to Act2, the game had to "reorganize" your inventory, because that's simply what it does after every act. It deletes all info about Act1, and creates new files for Act2. During this process your weapon name changed to what it was meant to be called in 1.43.
Just a theory...