Gmap Error "Javascript is required to view this map" when embedding the node in another node
GUnload is part of the Gmap API. Are you loading the Gmap js files served by Google?

The error would happen if the JS file from Google is:


Missing.
Has not been parsed when the code giving the error is executed.


To give a more thorough answer more details are needed.

Update  

The Gmap module is a bridge to the Gmap JS API that Google has created. The actual Gmap JS API is not included in the module itself but is served by google. It's included using the following line:

drupal_set_html_head('&lt;script src="'.
  check_url(url('http://maps.google.com/maps', array('query' =&gt; $query))).
  '" type="text/javascript"&gt;&lt;/script&gt;'
);


The error you are getting, it is caused by the lack of the above JS file, or because it's loaded after the gmap module JS code is run.