Mon Oct 29, 2012 3:20 pm by lax
Nah you're describing the problem perfectly. You said you run the launcher, and then you use ISBoxer for the second account. It's not going to work like that because ISBoxer has to be handling both instances of Diablo 3.
You need to set up a Character Set for multiple Characters (e.g. using the Quick Setup Wizard), and then launch the team. Each instance of the game will be launched for you. The first time you launch with ISBoxer it might take a minute or two to copy the cache, but after that it should take the normal amount of time to load.