Open up web.config file, and find
<!-- set code access security trust level - this is generally set in the machine.config
    <trust level="Medium" originUrl=".*" />
     -->
and change it to
<!-- set code access security trust level - this is generally set in the machine.config -->
    <trust level="High" originUrl=".*" />

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Or-Rouge Team Or-Rouge
Personally recommend Hostgator for hosting single or multiple DotNetNuke Websites.
DotNetNuke Tips and Tutorials
Install DotNetNuke to Godaddy root
DotNetNuke Türkçe Hakkinda Hersey

Rename; DotNetNuke.Modules.XML.dll to DotNetNuke.Modules.XML.dll.old
and DotNetNuke.Modules.XML.SqlDataProvider.dll to DotNetNuke.Modules.XML.SqlDataProvider.dll.old

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Or-Rouge Team Or-Rouge
Personally recommend Hostgator for hosting single or multiple DotNetNuke Websites.
DotNetNuke Tips and Tutorials
Install DotNetNuke to Godaddy root
DotNetNuke Türkçe Hakkinda Hersey

Hi

Did you just install ‘Ultra Media Gallery 3.0 Standard Edition’?
If so you can do the rename trick in the Bin folder from before, and rename the following files to .old:
BizModules.Decryption.dll -> BizModules.Decryption.dll.old
BizModules.UltraPhotoGallery.dll -> BizModules.UltraPhotoGallery.dll.old
BizModules.UltraPhotoGallery.SqlDataProvider.dll -> BizModules.UltraPhotoGallery.SqlDataProvider.dll.old

It worked for me!