Oh about that. There's a strange fix for that. The recent update might have fixed this already, but if not, here you go. If you have an alternate character on another account that has been able to rebirth before the update screwed it up, you just follow these series of steps.
1.) Start the Mabinogi client manually instead of going through the website log in.
2.) Log into other account, select free rebirthable character, and click the rebirth button
3.) Go through the normal procedures to do a free rebirth up until Nao asks you if you're sure you want to rebirth. Select no when she asks for this confirmation.
4.) You will be logged into the game world. Log back out into the character select screen and disconnect your internet.
5.) After a while, Mabinogi will notice you're not connected and kick you to the login screen again. If you didn't log in through the website, you'll see the log in form again instead of a big Start button. Log in to your account with the bugged rebirth character.
6.) Select the character you would like to rebirth and click the rebirth button. You should now be able to do a free rebirth.
I really wonder how people found this out but I'm not gonna question it. I've done this for two of my characters and it works.
Also, Soot Sprite, i really don't think lightning chaincasting is a good idea. Waste of mp in my opinion so just stick with your ice wand.