I am having problems using Tk::MListbox on windows vista. The module works perfectly using the same version of ActivePerl on windows XP.
The problem I have found is to do with the callbacks used to update each Tk::Listbox that Tk::MListbox uses.
Firstly Tk::MListbox does not use Tk::Listbox directly, instead it derives Tk::CListbox from Tk::Listbox and adds the functionality to call a '-updatecommand' callback whenever something happens to it. The problem arises in the functions that initiate the '-updatecommand' callback.
It uses ($w being a reference to the Tk::CListbox object)