It turns out that a community manager from the beta whose name I'm still not mentioning reads my blog, and wrote me an e-mail to ask for details, then wrote me another e-mail with a technical solution. The problem was not that companies launcher, but a corrupt file in Microsoft's .NET Framework. A problem with Microsoft software, who would have thunk that? :)
So not only are my beta starting problems solved, I am now also *seriously* impressed with that companies customer service. I'll tell you more about the game once the NDA is dropped.