Microsoft's Net Frameworks Service packs can be a pain to put on, not only do some take forever, but I have had problems putting them on. They fail to install. I found that this tool "dotnetfx_cleanup_tool" helps. It will uninstall all the Net Frameworks software, which allows you to start new and put them back on one at a time which seemed to fix my problems. I had to uninstall both 2 and 3. After I uninstall-ed them, I re-installed, then put on the updates and it worked.