Cannot access host settings after upgrading to 5.3.0.
No errors during upgrade process.
Checked this thread on a similar issue in 5.2.0 and none of the solutions worked for me

http://www.dotnetnuke.com/Community/Forums/tabid/795/forumid/107/threadid/342569/scope/posts/threadpage/1/Default.aspx

Checked my web.config settings as described in the thread and everything looks perfect.
Checked with my hosting provider that they are running .NET 3.5 SP1 and they are.

Response from hosting provider:
"1) NET Framework 3.5 SP1 is already installed and working on server.
2) We cannot assign full trust level. however we can assign medium trust level to subdomain.
3) You are using the latest version of DDN , may be this error is due to new version."

What could be cusing this?

Code error, file permissions, a bug in the upgrade package?

Stack trace dump:

Error: Host Settings is currently unavailable.
DotNetNuke.Services.Exceptions.ModuleLoadException: Property accessor 'filteredkey' on object 'VB$AnonymousType_1`2[[System.String, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089],[System.String, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]' threw the following exception:'VB$AnonymousType_1`2.get_filteredkey()' ---> System.Reflection.TargetInvocationException: Property accessor 'filteredkey' on object 'VB$AnonymousType_1`2[[System.String, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089],[System.String, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]' threw the following exception:'VB$AnonymousType_1`2.get_filteredkey()' ---> System.MethodAccessException: VB$AnonymousType_1`2.get_filteredkey() ---> System.Security.SecurityException: Request for the permission of type 'System.Security.Permissions.ReflectionPermission, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed. at System.Security.CodeAccessSecurityEngine.ThrowSecurityException(Assembly asm, PermissionSet granted, PermissionSet refused, RuntimeMethodHandle rmh, SecurityAction action, Object demand, IPermission permThatFailed) at System.Security.CodeAccessSecurityEngine.ThrowSecurityException(Object assemblyOrString, PermissionSet granted, PermissionSet refused, RuntimeMethodHandle rmh, SecurityAction action, Object demand, IPermission permThatFailed) at System.Security.CodeAccessSecurityEngine.CheckSetHelper(PermissionSet grants, PermissionSet refused, PermissionSet demands, RuntimeMethodHandle rmh, Object assemblyOrString, SecurityAction action, Boolean throwException) at System.Security.PermissionSetTriple.CheckSetDemand(PermissionSet demandSet, PermissionSet& alteredDemandset, RuntimeMethodHandle rmh) at System.Security.PermissionListSet.CheckSetDemand(PermissionSet pset, RuntimeMethodHandle rmh) at System.Security.PermissionListSet.DemandFlagsOrGrantSet(Int32 flags, PermissionSet grantSet) at System.Threading.CompressedStack.DemandFlagsOrGrantSet(Int32 flags, PermissionSet grantSet) at System.Security.CodeAccessSecurityEngine.ReflectionTargetDemandHelper(Int32 permission, PermissionSet targetGrant, CompressedStack securityContext) at System.Security.CodeAccessSecurityEngine.ReflectionTargetDemandHelper(Int32 permission, PermissionSet targetGrant) The action that failed was: Demand The type of the first permission that failed was: System.Security.Permissions.ReflectionPermission --- End of inner exception stack trace --- at System.Reflection.MethodBase.PerformSecurityCheck(Object obj, RuntimeMethodHandle method, IntPtr parent, UInt32 invocationFlags) at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks) at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture) at System.ComponentModel.ReflectPropertyDescriptor.GetValue(Object component) --- End of inner exception stack trace --- at System.ComponentModel.ReflectPropertyDescriptor.GetValue(Object component) at System.Web.UI.DataBinder.GetPropertyValue(Object container, String propName) at System.Web.UI.DataBinder.GetPropertyValue(Object container, String propName, String format) at System.Web.UI.WebControls.ListControl.PerformDataBinding(IEnumerable dataSource) at System.Web.UI.WebControls.ListControl.OnDataBinding(EventArgs e) at System.Web.UI.WebControls.ListControl.PerformSelect() at System.Web.UI.WebControls.BaseDataBoundControl.DataBind() at DotNetNuke.Modules.Admin.Host.HostSettings.BindModuleCacheProviderList() at DotNetNuke.Modules.Admin.Host.HostSettings.BindData() at DotNetNuke.Modules.Admin.Host.HostSettings.Page_Load(Object sender, EventArgs e) --- End of inner exception stack trace ---

My apologies about posting re. this in the other threads.

I initially googled the issue and found those threads and replied there. There were only about 3 results worldwide on google that seemed to discuss this exact problem.

It was only after viewing the full list of topics that I realized the upgrade section would be the the most appropriate place to post as this is essentially an upgrade issue.

I upgraded from version 4.9.3. During the upgrade process all providers, modules etc reported 100% success.

Everything  that I have had a chance to check thus far on the  web site seems to be working apart from the host settings.

Thanks Sebastien,

That is good news (5.3.1 was not available yestrday yet, so I'm very glad that it became available so rapidly)

I'm going to try the upgrade to 5.3.1 and hopefully that will resolve the issue.

Some addtional info:

I have confirmed with the web hosting provider that the application is running under medium trust, and that NetWork Service has been granted read/write permissions on the root folder. (Read/Write should be sufficient, not so?)