I'm having a really interesting problem, here. The FORM tag is being stripped out of the sidebar.php file for an optin box that has worked for over a year now. This client's site: http://itsallaboutwomen.com/ has had a functioning email opt-in form in their sidebar in a text widget.
Recently they asked me to upgrade the site to 3.1.3 so they could have a custom post_type archive for their affiliate store. This is when the problem began. http://dev.itsallaboutwomen.com/
After upgrading to 3.1.3 and creating the custom archive and taxonomy templates for their affiliate store, the opt-in box in the top right of the side bar now works on every page EXCEPT the archive and taxonomy template driven pages. http://dev.itsallaboutwomen.com/store
I tried shutting down all plug-ins. No dice.
I tried eliminating the text-widget and just hard-coding the FORM into the sidebar, since the same sidebar is used site wide. No dice.
Anyone have any ideas?