Ok, this only applies to those of us using the Academy Mod Package...
Shopping at NPCs that sell the event chocolate or being sent chocolate will crash your game if you are using the Academy Mod Package (at least 2.7.1 does).
If you want to keep the mod on and aren't sent any chocolate, just avoid being sent any and do not shop at Grocery store NPCs that sell it.
If you are sent it, you will not be able to login under that character after the crash since it keeps trying to give you the chocolate after each crash, thus causing another one.
To resolve this, uninstall the patch until Yoshirou makes a fix for it. I am sure though that Yoshirou will find out about the crash though before he even reads this.