Lol I agree...Corporate fire walls will be configured on the server your works pc is using as a gateway to the external internet.
In simple terms the route you are taking is probably like this :-
You at your desk -> *Your 'workstation'/Pc -> The 'server/Corporate PC' -> Firewall running on the 'server/corporate PC' -> Gateway/Main Hub(Router) -> a local ISP -> the rest of the world (the internet as you know it at home).
In short, at the point you are trying to access the internet *your worksation/PC, the firewall will be preset to authorise your worksation/PC access the ISP/internet and if so, it will no doubt be set to authorise only some sites. For example most companies may allow a request from
Google (if you're lucky) but not
Poker.com - Free Online Poker Games, Tournaments, Rules & News.
In short you need to get your PC authorised on the servers firewall (which may even be a dedicated firewall hardware kit).
Now there is one little trick you could try...but I cant guarantee it will work on your system as the administrators may have disable the function.
What I have done in the past with my bosses permission...and I can not stress enough your must have permission from your boss or system administrator. Buy a usb wireless dongle and see if you can find a hotspot (free wi-fi connection) or a bluetooth dongle and use your mobile (if bluetooth enabled to access the internet.
I would imagine that if your company has some savi and that the system is securely setup the usb/bluetooth or internet access will be disabled by the administrator and not accessible on your user login.
I cannot stress enough I am not responsible for the outcome of your actions.
Anything more than this would more likely construde hacking, misuse of company systems -> gross misconduct -> sack/P45
Personally give the net a rest -> do some work -> get paid -> buy a mobile phone with internet access or wait till lunch time
Hope this educative bit helps
I am sure there are smarter suggestions but my novice ability does not yield hacking main frames and I certainly would not give it a go !!!!