Observe_field not working with Internet Explorer

I have the following observe field in one of my rhtml files:

<%= observe_field(“order_plan”, :frequency => 0.2, :url => {:action =>
:update_list}, :with => “id”) %>

this works fine in firefox but Internet Explorer (6 and 7) causez my
code to fail.
For some reason when the observe_field calls the update_list it passes
the value of null for id

…, “id”=>“null”, …

Does anybody know why Internet explorer is doing this?

Thanks,
James

the mystery continues. I got rid of the observe field and changed it to
an onchange event in the select item but it still does the same.

Although i did notice it only returns null the first time, any further
onchange events cause the right id to be passed.

has anybody else has a similar problem?