Nested observe_field and IE

Hello,
Inside a view i have a list of nations, the drop-down is "observed" and
at any modification of this list an other nested list (with a regions
list) will be updated, that is itself observed and that update an other
nested list of provinces.
When i modify the nation at the beginning the regions and provinces are
correctly updated, but when the region is automatically updatet its
modification will be revealed by its observer and that read a "null"
value (as a string) and an error will be generated.
This happened ONLY using Internet Explorer, not using Firefox or Safari.

Any idea?
Thanks!

Iwan

Sorry for my poor english :slight_smile: