Never got that far looking for bugs concerning RowSource. There's only one advantage of that property: It allows Columnheads.
If you don't need them, you're much better off using the list-property. It allows you either fill it by arrays or refering to ranges, you can remove, add, modify, ... whatever you want.

If you need headers you might be interested in the ListView-Control, that one even provides additional options - though more difficult to handle than the common ListBox.