download of an element in the browser portion of the launcher failed, resulting in an unrecoverable script error.

The more common culprits are security (new version detected, need to update the enable/allow rule to recognize the new version) and SSL/TLS support issues (run inetcpl.cpl in the search/run box, go to the advanced tab and scroll down the list--make sure all SSL/TLS options are active).

Otherwise, something else is likely interrupting the download process when it is trying to pull information through the frontier.ffxiv.com server. May want to run a malware/AV scan.