have you tried reinstalling windower(none dev)?? with this one you download on the main page this link http://windower.net/Windower4Setup.exe
have you tried disabling your antivirus??(this is just a test and can be re-enabled after test) if it will load with av disabled you will need to add an exception
are you on the admin account??
what is your ffxi install folder (the default is)on 32 bit systems C:\Program Files\PlayOnline on 64 bit systems its C:\Program Files (x86)\PlayOnline
if yes to the above then the only thing i can think of is
1. your updates for windower were bad -- to try and fix delete the windower/updates folder then run windower again
2. for some reason something on your comp does not like windower