GibLit

doublepost... ignore

The exact same thing is happening to me. Have you installed the official HD texture pack? This started happening for me after I had installed it, so I'm wondering if it has anything to do with that. Before then, my launcher would go through the mod updates without any problems. I can still play the game through the SKSE launcher, but the vanilla launcher is the only way I can install future mods from steam as far as I know.