jQuery multi select plugin "selectList " doesn't add new options when the list is updated

jQuery multi select plugin "selectList " doesn't add new options when the
list is updated

I am using http://odyniec.net/projects/selectlist/usage.html plugin to
style Select boxes.
It adds little styling to the multi-select boxes and it looks cool.
I have a function which updates one of the select inputs with new options
but those new options doesn't get updated.
Ex: I have two multi-select inputs, based on the selections of 1 select
box, The value of second select box gets updated, But once i initiate this
plugin.., Even after the original select box gets updated, The plugin
doesn't update itself.
Is there a way to re-initialize the plugin on demand?
I tried to use their API Methods listed here
http://odyniec.net/projects/selectlist/usage.html#api-methods but i get
this error : TypeError: a.replace is not a function