So……you can connect to your VPN server and access you corporate network services but not the internet and then you disconnect from your VPN server and can access the internet but not the corporate network services.
I hop that is the correct surmise…… :S
Your issue sounds like your VPN server is sending you a default route back so all your traffic goes into your office. The issue then is with split tunnelling or the routes being advertised to you. Resolving either of these problems will ensure you can use both the corporate network services and your internet connection.