Inserting Attributes - Redirects to Admin Main Page

I've searched and can't find this particular problem. I'm not getting any error messages when I try to insert attributes, but it's redirecting back to the main admin page (and upon checking, it hasn't added the attributes to my product).

Just had an upgrade done from 1.3.9 to 1.5.1

Symptoms are typical of using non-1.5.x versions of admin files on a v1.5.x site. ie: your attributes_controller.php (or any other files which are redirecting to admin home page) haven't been upgraded to properly change all FORMs to be POSTs instead of GETs, and to use zen_draw_form() instead of just raw <form> tags. These changes are necessary in order to properly secure the data being submitted and processed, and to prevent security and XSS and CSRF attacks.
All the original ZC files for v1.5.1 already have all these changes made in them. But if you're using older files from older versions (or from plugins designed for older versions) then you'll run into those kinds of symptoms.

Thank you, DrByte

So attributes_controller.php ... would it be safe to upload that from the new version? And is there anything else I need to upload (concerning this issue)?

The guy who did the upgrade fixed it. I don't know how...probably just uploaded the new attributes_controller.php file.