userForm listBox being double-loaded

Howdy, Folks:

I'm having problems loading data into a listbox. When the form first opens, it loads the data twice. I can then kill the form and restart it and the data is in there three times. I can't see any loading problems with the userForm_initialize routine. How can I ensure that the listBox is empty before I start adding data? This would also seem to be necessary prior to loading a different set of data into the form - correct?

Any ideas?

TIA.

Bob