Unfortunately when using the network-manager-pptp package there is a bug with one of the network packages that prevents anyone with a static IP from succesfully connecting to a VPN server. When you left click your network icon you should see one of your network connections as selected. If they are all greyed out then you will suffer from this VPN issue. Unfortunately at the time of writing there is no fix other than to set your network connection from a static IP to roaming mode. Some people have suggested that Interpid Ibex will have a fix for this problem.