Cannot Access the internet on my Mac

Question

I have a MacPro, running 10.5.1 (although when this problem began it was probably a newer version the OS if there was one). I moved offices about 2 months ago-- same facility, same network. After one day in the new digs, my internet and network access (wired) stopped working. That has lead down a long path including hours on the phone with Applecare, one visit from a certified mac repairman, several archive and installs, hundreds of dollars of tech time by the company network engineers, and a month and a half of lost productivity.
*Internet Access:*
A wireless router has been installed, and my airport connection is set to the 192. schema. The Airport status window shows that I'm connected to the right network and full strength, however I still can't access the internet when I'm booted Mac OS. I've tried both Safari and Firefox. I can access the internet only when booted in Windows XP.
*Office Network Access:*
At this point, via manual configuration in Network Preferences, I have sketchy access to the office shares in both Operating Systems through a wired connection. When I'm in Leopard though, I have no access to the internet and no access to the printers on the network. In Windows XP, I have access to everything, even though XP is using the same hardware to do it. There seems to be something in my Mac OS blocking IPs. This conclusion was reached due to the fact that the office share I can access are recognized by name, but internet and printers are recognized by IP, hence, I can't use them.
Network Diagnostics says my "internet connection appears to be working correctly" with all green lights on the left side, but whenever I try to browse the internet, it says the same thing but the "ISP," "Internet," and "Server" items under Network Status all say Failed with the red lights.
The Office Network Engineer, anyone I talk to at Applecare, and I are all baffled. I'm the only Mac in the company, and I'm a luxury as a designer here. No one else is having these problems, and I'm now a month and a half behind. Things aren't looking good.
Can anyone out there help me...please?
*Other important details:*
-Office Server is Windows Server 2003 R2
-Every test that the Network Engineer has run on the server (Windows Server) has come up clean.
-I can't ping any IP's from my Mac Pro
-Traceroute yeilded the same results as everything above
-I can only access shares by the names assigned to them
-The network DNS could not Ping my Mac

Answer 1

"I have an ethernet cable in port 1 on my computer. That is configured manually to access ther office network."
Do you have a "real" IP address or a private (192.168.x.x, 10.x.x.x, 172.x.x.x) IP address?
"The wireless router was connected to the company server only for the purpose of getting me online through Airport because I couldn't access it using an ethernet connection"
Could not access it because their network security blocked you by intent, or had some unknown technical difficulty?
Unless you are blocked by intent or ommission (if they have to explicitly allow your machine) I can think of no technical reason why your wired connection should not both get you on their network and on the internet in general. You should not need to be dual homed (though dual homing should work as well).
Please answer the questions above when you can - I think solving the wired LAN issue will be easier if you are not being intentionally blocked.