I was in the middle of updating FFXIV for Stormblood and got the following error
unable to complete version update 30437
While looking at the launcher, I could see that it said updating ex2 - ##(version numbers) if you are able to see this as well, what you want to do is go into your
FFXIV install folder \SquareEnix\FINAL FANTASY XIV - A Realm Reborn\game\sqpack Look for the ex2 or whatever it is that the launcher is trying to update right before you got your error message (should say on the frozen launcher screen still)
Rename that folder to -old or whatever you want. End the process for the launcher if its still up, and relaunch the game. It should restart the download.

Just thought I would add my resolution to anyone else having the same issue.