Report Builder Report Download 401 Unauthorized Error

Environment:-
Server1 -- SQL services, SQL reporting services all 2008 R2 64bit, SharePoint installation 2010 and Reporting services add-in

Server2 -- SharePoint installation with Central Administration hosted 2010, Reporting services add-in .

Issue:- While downloading Report Builder report Externally (from Internet) it does not download and gives a "Cannot Retrieve error"

Error:- PLATFORM VERSION INFOWindows : 5.0.2195.262144 (Win32NT)
Common Language Runtime : 2.0.50727.42
System.Deployment.dll : 2.0.50727.42 (RTM.050727-4200)
mscorwks.dll : 2.0.50727.42 (RTM.050727-4200)
dfdll.dll : 2.0.50727.42 (RTM.050727-4200)
dfshim.dll : 2.0.50727.42 (RTM.050727-4200)

SOURCESDeployment url :
http://URL/ReportServer/ReportBuilder/ReportBuilder.applicationERROR SUMMARYBelow is a summary of the errors, details of these errors are listed later in the log.
* Activation of http://URL/ReportServer/ReportBuilder/ReportBuilder.application resulted in exception. Following failure messages were detected:
+ Downloading http://URL/ReportServer/ReportBuilder/ReportBuilder.application did not succeed.
+ The remote server returned an error: (401) Unauthorized.
COMPONENT STORE TRANSACTION FAILURE SUMMARYNo transaction error was detected.WARNINGSThere were no warnings during this operation.OPERATION PROGRESS STATUS* [08/05/2008 09:33:39] :
Activation of http://URL/ReportServer/ReportBuilder/ReportBuilder.application has started.

Tried and tested
So many blogs and articles online on this issue that I have lost count how many read and how many times I might have deleted and recreated web applications. As most of the articles and blogs suggest to enable Annonymous Access on the ReportBuilder Virtual directory in IIS, but SQL 2008 reporting services does not create this Virtual directory in IIS so how do we give annonymous access??? Broken my head on this issue with my colleagues and lot of hours reading long msdn and technet articles but all in vain...

Resolution:-
1. Browse to Central Administration of SP 2010
2. Application Management
3. Manage Web applications -> Select the Web Application which will be used for SSRS
4. Select Authentication Providers -> Select "Enable Annonymous Access" checkbox
5. Click Ok.

This will setup the most required annonymous access for the virtual directories in IIS and Report builder will start downloading from Internet also. Hope this helps to many out there. Also to mention our SP site was also configured with Kerberos and SSL using a Hostheader.