It seems that some few DotnetNuke configurations are not able to resolve Net.Permissions to System.Net.Permissions.
Xml 04.03.02 is a source based module, so it is easy to fix.Please edit app_code\xml\components\utils.vb and change the line 96 to
Return System.Security.SecurityManager.IsGranted(New WebPermission(NetworkAccess.Connect, url))
Save and you are done. No special tools needed, it works also with notepad. No build or compilation required.
I apologize for all the trouble you might had. A new version will be posted to the release tracker within the next days. I am still not able to reproduce the issue on my systems. If any of you in trouble please contact me at stefan.cullmann@dotnetnuke.com?
Thank you