Column Sorting Disappears after Indexed Search

Hi,

User changes to Sent view (and other views like All Documents) and columns that are supposed to be sortable appear sortable with the little arrow head . User does indexed search in this view and the Sent view columns now become unsortable - arrow heads disappear !! Clearing search results brings the same columns back as sortable.

User preferences include Retain View Column Sorting as checked.

Performed fixup on user mail database with no benefit.

Thanks in advance.

Tahir Mahmood.