I have a DNN 8.0.3 installation with several sites up and running.
When using Image Manager to upload on insert images in the HTML module, it works just fine on 7 of 8 sites.
I just set up a new site using a new skin and Image Manager does not work. The window pops up when I click on the image link in the HTML editor but I get nothing.
Here are are the relevant lines from the Site Log:
Message: Unable to complete operation. An unknown error occurred. /Portals/8
InnerMessage: Object reference not set to an instance of an object.
at DotNetNuke.Providers.RadEditorProvider.TelerikFileBrowserProvider.AddChildDirectoriesToList(DirectoryItem radDirectory)
at DotNetNuke.Providers.RadEditorProvider.TelerikFileBrowserProvider.ResolveRootDirectoryAsTree(String path)