Please help with building new component

I've created a new webform component that introduces the "sort" field type.
The module uses drupal's build in drag'n'drop feature for selecting elements order (like in menu).

This is particularly helpful if you would like to have a field like this: "Please tell us which features of software X are most important for you".
Thanks to my component users can just rearrange the order of features the way they want.

All works great except for one small thing:
When component is rendered all it's items have default order (randomized or not - it doesn't matter). Users can rearrange items but each time they re-enter the page with "sort list", the previously selected order is lost and items are displayed in default order. This is very annoying because when a webform page has some other fields and validation of one of them fails, users have to rearrange items again. The real problem is that they may not notice that items they already rearranged are messed up again.

I've been trying to work around this but run out of ideas. Debugging whole webform module is what I would really like to avoid, so a little help from developers of webform module would be very appreciated :)

One ugly idea was to use $_SESSION var to store user selected order of items when my component is validated. Then use the data in render function to rearrange items the way user did earlier. Unfortunately _webform_render_component($component, $value = NULL) is invoked before component validation function :(