You haven't commented your code well enough for someone like me to be able to tell alot about what's going on.

I'm seeing me.dataset, which obviously isn't a standard property.

The error sounds like the dataset was never instantiated, only referenced. Therefore, when you are calling Clear(), your code fails because its trying to call a method from an object that doesn't exist yet.

Is your me.Listbox set to the same datatable you are trying to clear? If so, it may fire a second SelectedIndexChanged event. And that will cause you headaches..

post more details plz..