I just upgraded to Mac OS X 10.5.3, and after a double reboot, and logging into the machine, I just found out that it had broken the Cisco VPN Client 4.9.01 (0100) again! Initially, I thought that it was the CiscoVPN Error 51: Unable to communicate with the VPN subsystem rearing its ugly head again and I tried to rectify it by typing
sudo /System/Library/StartupItems/CiscoVPN/CiscoVPN restart
in the terminal. Well, it seemed to do the trick and I managed to login. However, when I launched Entourage 2008, connection to my Exchange server could not be established. 10.5.3 seems to have broken the Cisco VPN Client again! Will have to wait and see if this is fixed soon. I am NOT going to upgrade my macbook yet until Cisco releases a new version of their VPN client.