Listbox selected item un-highlights when moving to another pat of the form

Hi, I have a bit of a weird situation with a userform I have built. The form has numerous Listboxes that have row sources that are linked to dynamic named ranges and all works expected apart from two.

I have a 'fromdate' list box and a'todate' listbox and when I select a date from the list in the todate listbox the previously selected fromdate selection un-selects and the list returns to the top index value of zero (despite setting the top index to a different value in the firm initialize module).

I have checked my code and there are no 'change' triggers on these boxes and the click action just moves values into a worksheet.

I'm completely baffled and couldn't find a single reference to anything similar despite repeated Google searching.

I'm just hoping one of you guys can think of anything that might be causing this?

Thanks and sorry for the long winded post.