Since ioFTPD didn't change during your OS upgrade I'm going on the assumption that it's window's fault
In theory you can check the credentials used to automatically login to your share via: Control Panel\All Control Panel Items\Credential Manager. However, googling has suggested that there is an issue with mounting shares when done as a user who is an administrator. What's really interesting is that it looks like the behavior depends upon your setting for UAC (user account control). My guess is you might have disabled this under vista because it had so many annoying popups about everything, but win7/8 fixed most of that so you probably left it on. Search for "EnableLinkedConnections" and see if setting that registry entry fixes anything...