I got another wierd error today when I tried to upload a new module on one of my Dotnetnuke sites:

ExceptionSystem.ArgumentException: Invalid File or Directory attributes value. at System.IO.File.SetAttributes(String path, FileAttributes fileAttributes) at DotNetNuke.Modules.Admin.ResourceInstaller.PaDnnInstallerBase.CreateFile(String FullFileName, Byte[] Buffer) at DotNetNuke.Modules.Admin.ResourceInstaller.PaDnnInstallerBase.CreateModuleFile(PaFile File, PaFolder Folder) at DotNetNuke.Modules.Admin.ResourceInstaller.PaDnnInstallerBase.CreateFiles(PaFolder Folder) at DotNetNuke.Modules.Admin.ResourceInstaller.PaDnnInstallerBase.Install(PaFolderCollection folders) at DotNetNuke.Modules.Admin.ResourceInstaller.PaInstaller.Install()

Turns out that the system account (Network Service) did not have full permissions on the root folder of the installation. As soon as I set it correctly, this error disappeared.