Form elements added by AHAH don't work

I'm running into two problems with form elements added to by AHAH:

1. Elements with the #ahah property don't work unless Javascript settings are already on the page. So new elements with the #ahah property don't work.
2. A file upload element requires the form enctype attribute to be set to "multipart/form-data". Adding a new file upload element can set this attribute in the server's cached copy of the form, but it doesn't change the setting in the browser.

For my current project I hacked around the problem by adding AHAH settings for all possible form elements that might be added to the page and by adding the enctype attribute "multipart/form-data" even when the initial form contains no file elements. This seems like a bug in AHAH form processing.