Vista VPN internet browsing problem

I have a VPN issue when using Vista.

When I use VPN to connect to my office machine, I could not using Internet browsing or sending email any more. Looks like it tries to run the Explorer or Windows Mail by connecting to my VPN network. Once disconnect the VPN, internet and email programs are back to normal. When I check the Network and Sharing Center, diagrams as below:

When Not using VPN: myPCname ----> MSHOME ----> Internet (Green/Blue global)

When connect and Using VPN: myPCname ----> Multiple networks --X--> Internet (Grey Global)

Once disconnect the VPN network, everything back to normal as:
myPCname ----> MSHOME ----> Internet (Green global)

When I use the same structure and the same programs in Windows XP, everything works fine. I can use both VPN and Internet Explorer at the same time.

Could anyone knows how to resolve the problem? Thank you very much.