Windows – Unable to ping or access internet

I am setting up a private network. The server is Windows 2008 R2 with DNS installed and has a fixed external IP address. ipconfig outputs the following:

PPP adapter RAS (Dial In) Interface:

Connection-specific DNS Suffix . :

IPv4 Address. . . . . . . . . . . : 192.168.16.7

Subnet Mask . . . . . . . . . . . : 255.255.255.255

Default Gateway . . . . . . . . . :

Ethernet adapter Local Area Connection 2:

Connection-specific DNS Suffix . :

IPv4 Address. . . . . . . . . . . : 192.168.16.2

Subnet Mask . . . . . . . . . . . : 255.255.255.0

Default Gateway . . . . . . . . . :

Ethernet adapter Local Area Connection:

Connection-specific DNS Suffix . :

Link-local IPv6 Address . . . . . : fe80::5c6a:b01f:2d23:92f8%11

IPv4 Address. . . . . . . . . . . : FIXED IP ADDRESS

Subnet Mask . . . . . . . . . . . : 255.255.255.248

Default Gateway . . . . . . . . . : FIXED IP ADDRESS

Other machines on the network aquire IP address like 192.168.16.15. However, none of these machines can ping any public sever (e.g., www.yahoo.com) or has the internet connection.

Another note: All these machines can browse to a website until I installed Visual Studio 2008 and TFS Team Explorer on the server.

In response to Boden's question, here are outputs from various commands executed on a client machine:

ping www.yahoo.com:

Pinging www-real.wa1.b.yahoo.com [209.191.93.52] with 32 bytes of data:
Request timed out.
Request timed out.
Request timed out.
Request timed out.

ipconfig:

 Ethernet adapter Local Area Connection: 
Connection-specific DNS Suffix . : DomainName 
IPv4 Address. . . . . . . . . . . : 192.168.16.13 
Subnet Mask . . . . . . . . . . . : 255.255.255.0 
Default Gateway . . . . . . . . . : 192.168.16.2 

nslookup www.yahoo.com:

Server: UnKnown 
Address: 192.168.16.2 

Non-authoritative answer: 
Name: www-real.wa1.b.yahoo.com 
Address: 209.191.93.52 
Aliases:  www.yahoo.com
          www.wa1.b.yahoo.com

Please let me know if you need more information. Thanks.