May not be related but it's worth a try.
In C:\Users\{pc user}\Documents\My Games\FINAL FANTASY XIV - A Realm Reborn there are some FFXIV_CHR{random hex} folders, one for each char. Try renaming the one relative to your char (prepending a "_" for example) or all of them if you don't know which one it is and try logging in again. If it doesn't work, you can delete the newly created ones and rename the folders back.