Chained Select in a Dialog

Chained Select in a Dialog

Hi all,
I'm a bit of a noob when it comes to jQuery so I appolgise if I'm doing something stupid (which I probably am).

I've created a chained select using the plugin from http://www.appelsiini.net/projects/chained

The plugin seems to work well on its own but when I move it into a jQuery dialog box I get unusual results.  The first option I select works correctly but if I choose any primary options (other than the first) the second chained select is always blank and results in a disabled select box.

Move it out of the dialog and it works correctly.

Any ideas why this might happen?

Thanks in advance.