ERROR: When you log on to Microsoft Office Communicator: "Cannot Synchronize Address Book"

Note This issue occurs on the client-side. However, you have to configure the settings on the server that is running Microsoft Office Communications Server to resolve the issue. If you are not familiar with Office Communications Server, contact the server administrator.

To resolve this issue, you must have the Administrator permission on the server that is running Microsoft Office Communications Server.

Windows Server 2003-based server

Method 1: If the Address Book Files folder is on the computer that is running Communications Server

1. Click Start, click Run, type inetmgr, and then click OK.
2. Expand ServerName, expand Web Sites, expand Default Web sites, and then expandAbs.
3. Right-click Ext, and then click Properties.
4. In the Ext Properties dialog box, click to select the A directory located on this computer check box on the Virtual Directory tab, click Browse to select the Address Book Files folder, and then click OK.
5. Repeat steps 3 and 4 for Int in the Abs node.

Windows Server 2008-based server

Method 1: If the Address Book Files folder is on the computer that is running Communications Server

1. Click Start, click Run, type inetmgr, and then click OK.
2. Expand ServerName, expand Sites, expand Default Web sites, and then expand Abs.
3. Expand Ext and click on Files, in the Actions pane click on Basic Settings
4. Using the Physical path setting browse to the Address Book Files folder.
5. Click OK twice and close the IIS 7.0 Management console
6. Repeat steps 3 through 5 for Int in the Abs node.

Source: http://support.microsoft.com/kb/938286

HOWTO: Create Cisco VPN tunnel using native Mac OSX

Overview:
Yes, it can be done!! If you're sick of Error 51 when launching the Cisco VPN client on Mac OS X give this a shot.

http://anders.com/guides/native-cisco-vpn-on-mac-os-x/