I figured out today that neither the newform or editform work when you customize them. It's like they don't pass the values selected to the list or something. Here's my method for creating a custom form:
1. New aspx page
2. Insert Custom List Form (New/Edit/Disp)
3. Attach masterpage
4. Save under the list's folder.
When viewing either the New or Edit form in SharePoint Designer, when it tries to render the fields it gives me this:
"An unhandled exception has occured. Request for the permission of type 'System.Security.Permissions.SecurityPermission, mscorlib, Version=18.104.22.168, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed."
I'm not sure if this is normal or if this is specific to the problem I'm having.