Unable to Edit SP2010 Integrated SSRS 2008 R2 SP1 Server Properties in SSMS

I have a SharePoint 2010 Integrated instance of SSRS 2008 r2 SP1 10.50.2500.   The server behaves well and runs fine for all tasks with respect to reports, data sources, deployment of reports through Visual Studio, access to Report Builder etc, etc.   All is well

However, when I attempt to login to the SSRS server itself, using Domain Admin credentials and / or combination of running SSMS as Administrator, running SSMS as the SSRS Service Account, logged in as the SSRS Service Account, etc. etc.  I cannot edit any Server Properties through SSMS

I actually have two SSRS 2008 R2 SP1 instances like this (Test and Production) and the error is the same.  I would have thought that if there was truly an issue with SSRS config, it would have shown itself somewhere else along the line, but it doesn't.   I can connect to the Integrated instance with SSMS and browse everything (except Jobs for some reason) I only have this problem of being unable to EDIT Server Properties in SSMS.

The Advanced Server properties are not greyed out - I can edit them, but as soon as I try to commit the changes I get:

TITLE: Microsoft SQL Server Management Studio
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The permissions granted to user 'i:0#.w|domain\administrator' are insufficient for performing this operation. (rsAccessDenied) (Reporting Services SOAP Proxy Source)

For help, click: http://go.microsoft.com/fwlink/?LinkId=20476&EvtSrc=Microsoft.ReportingServices.Diagnostics.Utilities.ErrorStrings&EvtID=rsAccessDenied&ProdName=Microsoft%20SQL%20Server%20Reporting%20Services&ProdVer=10.50.2500.0

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ADDITIONAL INFORMATION:

The permissions granted to user 'i:0#.w|domain\administrator' are insufficient for performing this operation. (rsAccessDenied) (ReportingServicesLibrary)

For help, click: http://go.microsoft.com/fwlink/?LinkId=20476&EvtSrc=Microsoft.ReportingServices.Diagnostics.Utilities.ErrorStrings&EvtID=rsAccessDenied&ProdName=Microsoft%20SQL%20Server%20Reporting%20Services&ProdVer=10.50.2500.0

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BUTTONS:

OK
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These two servers (SSRS and SharePoint ) are operating in a Claims Based authentication environment.

After spending about 30 - 40 mins looking for answers, I noted that all the articles and forums seem to talk about solving the problem by running SSMS as Administrator (did not work) OR, making entries to the ReportServer permissions in a NATIVE environment.   Given that this is not a NATIVE environment, I do not know how to approach that issue, particularly when ALL other aspects of the Integrated setup appear to be working perfectly!!

Please help

Thank you

DWM