Image got error 500?

Is kind of strange, I never have problem when I do development in Visual Studio 2010.

Or after publish to my local iis7 and connect to the site directly with network ip 192.168.x.x. (using IE)

But when I access from DNS redirect, using some domain name.. Sometime some of the image will not display (from iis7 log it got error 500)... Then if I right click the image and choose Show Image to reload the image, it will show up properly again.

From Server2008 IIS7 Log
    2011-04-15 14:07:56 173.32.2.83 GET /MyASPProgram/Styles/title_bar_bg.png - 80 - 173.239.186.98 Mozilla/4.0+(compatible;+MSIE+8.0;+Windows+NT+6.1;+WOW64;+Trident/4.0;+SLCC2;+.NET+CLR+2.0.50727;+.NET+CLR+3.5.30729;+.NET+CLR+3.0.30729;+Media+Cen开发者_如何学Pythonter+PC+6.0;+.NET4.0C;+.NET4.0E) 500 0 0 109

I wonder if that's a problem with the iis7 setting? But is strange to work fine when access the network... Or it is just the DNS redirect problem?

Thanks in advance.

What authentication are you using?

I bet this is the classic double hop issue.