Unable to connect Outlook via RPC over HTTP

I'm running SBS 2003 with Exchange SP2

After configuring the Outlook client for RPC/HTTP I cannot logon, it used to work and something broke.

I ran testexchangeconnectivity.com test and this is what I'm getting

Testing RPC/HTTP connectivity
       RPC/HTTP test failed
      Test Steps
       
      Attempting to Resolve the host name mail.harvego.com in DNS.
       Host successfully Resolved
      Additional Details
       IP(s) returned: 63.207.xxx.xxx
      Testing TCP Port 443 on host mail.xxxxx.com to ensure it is listening/open.
       The port was opened successfully.
      Testing SSL Certificate for validity.
       The certificate passed all validation requirements.
      Test Steps
       
      Validating certificate name
       Successfully validated the certificate name
      Additional Details
       Found hostname mail.xxxx.com in Certificate Subject Common name
      Validating certificate trust
       Certificate is trusted and all certificates are present in chain
      Additional Details
       The Certificate chain has be validated up to a trusted root. Root = E=info@valicert.com, CN=http://www.valicert.com/, OU=ValiCert Class 2 Policy Validation Authority, O="ValiCert, Inc.", L=ValiCert Validation Network
      Testing certificate date to ensure validity
       Date Validation passed. The certificate is not expired.
      Additional Details
       Certificate is valid: NotBefore = 11/21/2008 3:12:41 PM, NotAfter = 12/14/2011 11:02:15 AM
      Testing Http Authentication Methods for URL https://mail.xxxxxx.com/rpc/rpcproxy.dll
       Http Authentication Test failed
      Additional Details
       Exception Details:
Message: The underlying connection was closed: The connection was closed unexpectedly.
Type: System.Net.WebException
Stack Trace:
at System.Net.HttpWebRequest.GetResponse()
at Microsoft.Exchange.Tools.ExRca.Tests.HttpAuthMethodsTest.GetSupportedHttpAuthMethods()
at Microsoft.Exchange.Tools.ExRca.Tests.HttpAuthMethodsTest.PerformTestReally()

The only thing I tried was to remove RPC component rest IIS and add it back. Didn't make any difference.

what else should I check?

thank you