Question : OCS Client error when trying to expand Distribution list members

We are getting an OCS Client error when trying to expand a Distribution list members
Cannot perform this action and the cause is unknown.  Contact your system administrator to investigate this problem

Here are the IIS logs related to Group Expansion
2009-11-17 20:01:39 POST /GroupExpansion/Int/service.asmx - 443 - Microsoft+Office+Communicator/3.0 401 1 2148074254 4
2009-11-17 20:01:39 POST /GroupExpansion/Int/service.asmx - 443 - Microsoft+Office+Communicator/3.0 401 2 5 1

Here are the errorsWeb Components Server Validation:
Check GroupExpansion       Failure
[0xC3FC200D] One or more errors were detected  

Check Http URL   URL: https:///GroupExpansion/Int/service.asmx
Received a failure HTTP response.: HTTP Response: 401 Unauthorized
Cache-Control:private
Content-Type:text/html; charset=utf-8
Server:Microsoft-IIS/7.0
WWW-Authenticate:Negotiate,NTLM
X-Powered-By:ASP.NET
Date:Tue, 17 Nov 2009 20:23:50 GMT
Content-Length:6653

Received a failure HTTP response.: Unauthorized
Suggested Resolution: Check whether the Web Server or Office Communications Server component is running and also listening on the specified url. If server is behind a load balancer, please make sure the loopback connection is allowed from load balancer FQDN.
Suggested Resolution: Check the Web Proxy setting in this machine and ensure that it is correctly configured

OCS 2007 R2 Enterprise
Server 2008 SP2

Answer : OCS Client error when trying to expand Distribution list members

After installing SQL Reporting, we had to disable ASP.NET Impersonation on all the OCS IIS directories.  

In IIS7:
click on the following directories:
ABS, AutoUpdate, GroupExpansion, PhoneConferencing, RGS, and Conf

Highlight the directory
Double-Click Authentication
Right-click > Disable ASP .NET Impresonation
restart IIS (iisreset)