I've had this happen to me only when I used a certain code. I found out it was because that code was deprecated. As soon as I removed it my game worked.
Another cause for this error could be because you went over the code limit; do you have a gameconfig.txt in your root?
Yeah
[Edit]: It was the SSBM Melee Air Dodge 2.1 code that kept causeing the exception (DSI) occured