A bit more info: Got this error for each module on the page after logging in as host, just now.

Unhandled error loading module. DotNetNuke.Services.Exceptions.ModuleLoadException: Unhandled Error Adding Module to LeftPane ---> System.Security.SecurityException: Request for the permission of type 'System.Security.Permissions.FileIOPermission, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed. at System.Security.CodeAccessSecurityEngine.Check(Object demand, StackCrawlMark& stackMark, Boolean isPermSet) at System.Security.CodeAccessPermission.Demand() at System.IO.Path.GetFullPath(String path) at System.Web.Util.FileUtil.IsSuspiciousPhysicalPath(String physicalPath, Boolean& pathTooLong) at System.Web.Util.FileUtil.IsSuspiciousPhysicalPath(String physicalPath) at System.Web.CachedPathData.GetConfigPathData(String configPath) at System.Web.CachedPathData.GetConfigPathData(String configPath) at System.Web.Configuration.WebConfigurationManager.GetWebApplicationSection(String sectionName) at DotNetNuke.Framework.Providers.ProviderConfiguration.GetProviderConfiguration(String strProvider) at DotNetNuke.Framework.Reflection.CreateObject(String ObjectProviderType, String ObjectProviderName, String ObjectNamespace, String ObjectAssemblyName, Boolean UseCache) at DotNetNuke.Modules.NavigationProvider.NavigationProvider.Instance(String FriendlyName) at DotNetNuke.UI.WebControls.SolPartActions.OnInit(EventArgs e) at System.Web.UI.Control.InitRecursive(Control namingContainer) at System.Web.UI.Control.InitRecursive(Control namingContainer) at System.Web.UI.Control.AddedControl(Control control, Int32 index) at System.Web.UI.ControlCollection.Add(Control child) at DotNetNuke.UI.Skins.Skin.InjectModule(Control objPane, ModuleInfo objModule, PortalSettings PortalSettings) The action that failed was: Demand The type of the first permission that failed was: System.Security.Permissions.FileIOPermission The Zone of the assembly that failed was: MyComputer --- End of inner exception stack trace ---

OK - looks like at least 3 of us are experiencing the same (or very similar) error. My host, in their attempts to fix the problem said:

"Setting the /dnntest application root into the appropriate application pool on the server has corrected the .NET backtrace you've seen previously. We apologise for any inconvenience this may have caused.

"For future reference and local reproduction of our environment, our .NET configuration uses impersonation so it's usually sufficient to give the IUSR change permissions over a DNN tree."

I must admit this is double-dutch to me, but sounds impressive! Unfortunately, I'm still experiencing the problem. I'm intending to do a complete fresh install on the weekend to see if the fix they did might work ok with a new install. But my hopes are not that high.

Can anyone please shed some light on this??? Or at least suggest some things that could be investigated or tried?

Decided to see if 4.3.7 makes any difference, again with a fresh install.

So, I cleaned out the database of all content except system info and deleted the installation folder contents. Made changes to web.config and uploaded to the hosted environment. Installation reported no errors. I was able to login as host. But when I clicked on the username (to change from the default password), the same old error came up - repeated below.

PLEASE PLEASE - any hints?????

  Description: The application attempted to perform an operation not allowed by the security policy.  To grant this application the required permission please contact your system administrator or change the application's trust level in the configuration file.

Exception Details: System.Security.SecurityException: Request for the permission of type 'System.Security.Permissions.FileIOPermission, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed.

Source Error:

[SecurityException: Request for the permission of type 'System.Security.Permissions.FileIOPermission, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed.]
   System.Security.CodeAccessSecurityEngine.Check(Object demand, StackCrawlMark& stackMark, Boolean isPermSet) +0
   System.Security.CodeAccessPermission.Demand() +59
   System.IO.Path.GetFullPath(String path) +98
   System.Web.Util.FileUtil.IsSuspiciousPhysicalPath(String physicalPath, Boolean& pathTooLong) +50
   System.Web.Util.FileUtil.IsSuspiciousPhysicalPath(String physicalPath) +23
   System.Web.CachedPathData.GetConfigPathData(String configPath) +465
   System.Web.CachedPathData.GetConfigPathData(String configPath) +243
   System.Web.CachedPathData.GetConfigPathData(String configPath) +243
   System.Web.CachedPathData.GetVirtualPathData(VirtualPath virtualPath, Boolean permitPathsOutsideApp) +132
   System.Web.HttpContext.GetFilePathData() +27
   System.Web.HttpContext.GetConfigurationPathData() +26
   System.Web.Configuration.HttpConfigurationSystem.System.Configuration.Internal.IInternalConfigSystem.GetSection(String configKey) +36
   System.Configuration.ConfigurationManager.GetSection(String sectionName) +107
   System.Configuration.ConfigurationManager.get_AppSettings() +29
   System.Web.Configuration.WebConfigurationManager.get_AppSettings() +5
   DotNetNuke.Common.Globals.GetDomainName(HttpRequest Request, Boolean ParsePortNumber) +75
   DotNetNuke.HttpModules.UrlRewriteModule.OnBeginRequest(Object s, EventArgs e) +4056
   System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +92
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +64

Server Error in '/dnntest' Application.

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Security Exception

Version Information: Microsoft .NET Framework Version:2.0.50727.42; ASP.NET Version:2.0.50727.42