Data loss has been an issue of varying occurence since the game came out. I will explain here why it happens and what can be done about it.
Why does it happen?
Unlike most video games, Castle Crashers doesn't save your progress onto the game system hard drive. Instead your progress is linked to your profile. It is similar to global statistic rankings for things such as Kill/Death ratio in First Person Shooters. Data loss occurs when your data doesn't properly load when connecting your profile to online. It is not due to any update or DLC. There are no accounts of this happening to offline players.
How to prevent loss.
Always check your Character Statistics before playing. This is located in the main menu. If your characters aren't at the level they should be then you are either experiencing Data Loss or the Character Copy Glitch. Data Loss will make all of your characters Level 1 and the Copy Glitch will give your characters the stats and items of another person. Sometimes you will get an error message saying something is wrong before the main menu starts up, pay attention and don't ignore these.
What to do.
Under no circumstances should you go past the Character Selection Screen.
If you are at the Character Selection Screen shut off your game system immediatley.
None of these glitches or errors will save so long as you don't go past the character selection screen. The game auto saves the moment you enter the world map, which is the first place you are at after selecting your character. Hence, all of your correct data and progress will be overridden the moment you start playing the game.
The solution is to sign out and sign back in into your XBL or PSN account. If this doesn't work then try turning off your console and starting it up again. Whatever you do don't start playing the game until all of your data is in order otherwise you will be stuck with the incorrect stats. If all else fails try deleting the game and redownloading it.
DLC not showing up.
If you notice all of your characters are in order except your DLC is not showing then simply check to make sure your hard drive is properly plugged in or redownload them. Playing with other characters without DLCs loaded will not affect them in any way.
Edited by The Forgotten Knight, 12 July 2012 - 08:51 PM.