I myself am receiving this problem, so its not a singular person issue.
I was alerted by my server provider Kerplunc Gaming, that Hack/Mine servers were available from them. Looking at the videos, being a Diablo fan, I said hell why not. First, trying it on single player, it's bloody amazing with a lot of potential.
Soured a little when I tried to connect to my server, resulting in what the OP has described. At first, it'll say logging in, then it will flash twice or so, then it will just show the dirt background. Shortly afterwards, white screen and alt + f4 to restart Minecraft.
Questioning Kerplunc, they told me it was a bug that will need fixed by next patch of the Technic Launcher. Its a little disheartening to see the OP hasn't received official word on this issue, because I'd love to confirm the bug and have a confirmation that it is being fixed/when the next patch for the Launcher is coming out.
