If you work a lot with VPNs, you will notice that, alas, with many VPN setups, once you log into VPN you can not browser the Internet on the same machine.
This is a VPN misconfiguration issue that has to do with being unable to resolve DNS, but if you'd rather fix it yourself than argue with a sysadmin, here's a simple solution:
Indicate custom DNS server for your connection (e.g. your WiFi connection). Google's free DNS servers (184.108.40.206 and 220.127.116.11.) or OpenDNS servers (18.104.22.168 and 22.214.171.124) are both excellent choices.