Since the problem in this thread:

https://social.technet.microsoft.com/Forums/office/en-US/a4f38375-f20e-4e56-a417-97ee5e2bf779/sm-portal-systemtimeoutexception-httprequesttimedoutwithoutdetail-over-wan-link?forum=systemcenterservicemanager

seems the same as the problem I have, you'd think the two solutions presented therein would solve the problem for me, but they don't. My SMPortal page loads into IE, but it throws this error at the bottom of the page (you can't read all of it): [TargetInvocationException]\nArguments \nDebugging resource strings are unavailable. .....

The SMportaltrace.log file has this in it:

Error,2015-07-10 13:39:32.3545582,System.Reflection.TargetInvocationException: [Arg_TargetInvocationException]
Arguments:
Debugging resource strings are unavailable. Often the key and arguments provide sufficient information to diagnose the problem. See http://go.microsoft.com/fwlink/?linkid=106663&Version=5.1.40416.00&File=mscorlib.dll&Key=Arg_TargetInvocationException ---> System.TimeoutException: [HttpRequestTimedOutWithoutDetail]
Arguments: http://servername:8080/ServiceHost/Services/DataAccessService.svc
Debugging resource strings are unavailable. Often the key and arguments provide sufficient information to diagnose the problem. See http://go.microsoft.com/fwlink/?linkid=106663&Version=4.0.50401.0&File=System.ServiceModel.dll&Key=HttpRequestTimedOutWithoutDetail ---> System.Net.WebException ---> System.Net.WebException
   at System.Net.Browser.BrowserHttpWebRequest.InternalEndGetResponse(IAsyncResult asyncResult)
   at System.Net.Browser.BrowserHttpWebRequest.<>c__DisplayClassa.<EndGetResponse>b__9(Object sendState)
   at System.Net.Browser.AsyncHelper.<>c__DisplayClass4.<BeginOnUI>b__1(Object sendState)
   --- End of inner exception stack trace ---
   at System.Net.Browser.AsyncHelper.BeginOnUI(SendOrPostCallback beginMethod, Object state)
   at System.Net.Browser.BrowserHttpWebRequest.EndGetResponse(IAsyncResult asyncResult)
   at System.ServiceModel.Channels.HttpChannelFactory.HttpRequestChannel.HttpChannelAsyncRequest.CompleteGetResponse(IAsyncResult result)
   --- End of inner exception stack trace ---
   at Microsoft.EnterpriseManagement.ServiceManager.Portal.ServiceCatalogSilverlightModule.Models.DataProvider.<>c__DisplayClass1.<FetchAllServiceOfferings>b__0(Object sender, AsyncDataCommandCompletedEventArgs`1 e)
   at Microsoft.EnterpriseManagement.Presentation.DataAccess.AsyncDataCommandBase`2.<>c__DisplayClass2.<CompleteCommand>b__0(Object )
   --- End of inner exception stack trace ---
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks)
   at System.Delegate.DynamicInvokeImpl(Object[] args)
   at System.Windows.Threading.Dispatcher.InvokeImpl(DispatcherPriority priority, Boolean useFastPath, Delegate d, Object[] args)
   at System.Windows.Threading.DispatcherSynchronizationContext.Send(SendOrPostCallback d, Object state)
   at Microsoft.EnterpriseManagement.Presentation.DataAccess.AsyncDataCommandBase`2.CompleteCommand(Object sender, AsyncDataCommandCompletedEventArgs`1 e)
   at Microsoft.EnterpriseManagement.Presentation.DataAccess.AsyncDataCommandBase`2.OnCommandCompleted(Object sender, Exception exception)
   at Microsoft.EnterpriseManagement.Presentation.DataAccess.DataGatewayBase.CompleteAsyncDataCommandWithError(AsyncDataCommand command, Exception exception)
   at Microsoft.EnterpriseManagement.Presentation.DataAccess.ProxyDataGateway.ProxyExecuteCompletedHandler(Object sender, ExecuteCompletedEventArgs e)
   at Microsoft.EnterpriseManagement.Presentation.DataAccess.ProxyDataGateway.<>c__DisplayClass4.<GetClientProxy>b__3(Object sender, ExecuteCompletedEventArgs args)
   at Microsoft.EnterpriseManagement.Presentation.DataAccess.Proxy.ServiceReference.DataAccessServiceClient.OnExecuteCompleted(Object state)
(this info seems to repeat over and over)

This seems timeout related but the fixes in the technet article above didn't fix my case. Note I only had 5 xap files, not 6. This is Foundation 2010 on Server 20

Using this page, I seem to connect to the DataAccessService:

https://technet.microsoft.com/en-us/library/hh667347.aspx

The URL background is white, the page loads without warnings. The page in the TN article has different wording than my page but it looks similar (white background and tan blocks with code samples). This DataAccessService page matches the DAS page on a totally different SCSM install on a different network that I have.