Are you using Sandbox or Prod Sandbox? I just tried it in prod sandbox and could add a gadget without any problems using the developer page (and I used a test account that's like any ordinary account, not a special Google account or anything like that).
For reference, my XML looks like this: <?xml version="1.0" encoding="UTF-8"?><Module> <ModulePrefs title="Test Application v0.3" author="Bruno Oliveira" author_email=" your_real_email_h...@example.com" description="A test application." screenshot="http://www.linux.ime.usp.br/~btco/tmp/typechampion.png" thumbnail="http://www.linux.ime.usp.br/~btco/tmp/typechampion-thumb.png"> <Require feature="opensocial-0.8" /> <Locale lang="en" country="us" /> </ModulePrefs><Content type="html" preferred_width="970"><![CDATA[ Hello, this is a test app. 3 ]]></Content></Module> Thanks! - Bruno Oliveira (Google) -- You received this message because you are subscribed to the Google Groups "orkut Developer Forum" group. To view this discussion on the web visit https://groups.google.com/d/msg/opensocial-orkut/-/j9zNeveAaSIJ. To post to this group, send email to opensocial-orkut@googlegroups.com. To unsubscribe from this group, send email to opensocial-orkut+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/opensocial-orkut?hl=en.