Oh that might be the problem. Why not use same dataset in both cases?
Also when you let the program run and it show the error dialog if you click on retry then it will take you to the line at which crash occurs. If you look at the stack trace then you might be able to find the offending code line.
i used the smaller set to make sure my algorithm was right. when the unhandled exception msg box appears, i click on OK and takes me
some kind of assembly code: 7C812AFB pop esi.......i really don't know how to debug this