MultiSelect field values get wipes when using AHAH behaviors

Here is a workflow to reproduce the error:

- Create a new content type with FileField & ImageField and set it for unlimited number of images + use Multiselect & Content Taxonomy for easy selection of taxonomies.
- Enter a node title, select few taxonomy values at the Multiselect box.
- Upload an image file (everything is ok so far).

From this point I found 2 options to reproduce the error:

Option 1:
- Add another image file upload field
- Upload the second image file, which automatically validate the form and erase all of the selected values from the Multiselect box (other fields keep their values).

Option 2:
- Click on the "Remove" button for the first file which also automatically validate the form and erase all of the selected values from the Multiselect box.

By the way I'm running Drupal 6.10.
Also, you can use the Upload module as well to reproduce the error (just set it to unlimited number of files and the second file will reproduce it).

Thanks & cheers!