Okay, which version is displayed in the top left corner of the launcher? If it is "1.1.8.1 | A57", do the following:
Close the launcher and open up this file with a text editor like Notepad++:
C:\program files(x86)\Steam\Steamapps\common\Skyrim\EnderalLauncher\system\config\conf.sur
Find the line sCurrentVersion
If it displays
change it to something like
Save the file, run the launcher, close the launcher again. Open up the file in the editor again and change back to 1.1.8.1 and you should be good to go.
If that does not work change the value to 1.1.0.0, save and run the launcher again, and download the updates again.