Open up Desktop Manager, you don't need to have your phone connected for this.
Click Help and select About Desktop Manager.
Click on the tab labeled Device Software.
Something doesn't match up then. You have an Alltel branded 8130? And you installed the Alltel version of the OS for the 8130? Then it should not give you a no additional software error message in the app loader... I can't think of a reason why it would still give that error.
So, really stupid question. What applications are you trying to install when you're using the app loader? I'm sorry if that's a dumb question...just curious.