Error Webpages, no online functions - ISP, server, router?

How about reentering the Routers Setup and changing back to the defaults then resetting it with only the basic settings. Reboot the router and then see if it works now. If it does continue to make one change at a time till it is either fully set to your Security Level or it stops working.

Then the last change that you made is the problem and you can workout what is required from there.

Of course I'm assuming here that the cables between the Modem, Router and switch are all OK and not damaged. Doesn't sound as if they are but hitting them with a cable tester may show something interesting like a Crossover Cable or something like that.

Col

Repairing Damaged Winsock2
The symptoms when Winsock2 is damaged shows when you try to release and renew the IP address using IPCONFIG.
And you get the following error message:
An error occurred while renewing interface 'Internet': An operation was attempted on something that is not a socket.
Also Internet Explorer may give the following error message:
The page cannot be displayed Additionally, you may have no IP address or no Automatic Private IP Addressing (APIPA) address, and you may be receiving IP packets but not sending them.
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If you have WindowsXP with Service Pack 2, there is a one line command you can run to reset the winsock2 registry entries
netsh winsock reset catalog
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There are two easy ways to determine if Winsock2 is damaged:
From the XP source files, go to the Support / Tools directory
Winsock Test Method 1

Run netdiag /test:winsock
The end should say Winsock test ..... passed
Winsock Test Method 2

1.Run Msinfo32

2.Click on the + by Components

3.Click on the by Network

4.Click on Protocol

5.There should be 10 sections if the Winsock2 key is ok
MSAFD Tcpip [TCP/IP]
MSAFD Tcpip [UDP/IP]
RSVP UDP Service Provider
RSVP TCP Service Provider
MSAFD NetBIOS [\Device\NetBT_Tcpip...
MSAFD NetBIOS [\Device\NetBT_Tcpip...
MSAFD NetBIOS [\Device\NetBT_Tcpip...
MSAFD NetBIOS [\Device\NetBT_Tcpip...
MSAFD NetBIOS [\Device\NetBT_Tcpip...
MSAFD NetBIOS [\Device\NetBT_Tcpip...
If the names are anything different from those in this list, then likely Winsock2 is corrupted and needs to be repaired.
If you have any 3rd party software installed, the name MSAFD may be changed.
There should be no fewer than 10 sections.
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To repair Winsock2

1.Run Regedit

2.Delete the following two registry keys:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Winsock
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Winsock2

3.Restart the computer

4.Go to Network Connections

5.Right click and select Properties

6.Click on the Install button

7.Select Protocol

8.Click on the Add button

9.Click on the Have Disk button

10.Browse to the \Windows\inf directory

11.Click on the Open button

12.Click on the OK button

13.Highlight Internet Protocol (TCP/IP)

14.Click on the OK button

15.Reboot
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If you've found yourself hitting DNS errors or 404 pages in your browser but you know your net connection is working fine, it might be time to flush and restart Windows' DNS cache. The How-To Geek shows how to do this in three command line entries, although you might only need the first to see results. After launching a command prompt as an administrator and closing down Firefox (which has its own DNS cache), enter the following:

ipconfig /flushdns
net stop dnscache
net start dnscache

An easier and quicker way of doing this in XP is to:
1) go to Start
2) go to Run
3) Type: services.msc
4) click Enter.
5) Then locate "DNS Client"
6) Right click on it.
7) From there, click Restart
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Put into a .bat file.
@echo off
echo .*** RUNNING IPCONFIG /FLUSHDNS ***
pause
ipconfig /flushdns
echo .*** STOP THE DNS CACHE ***
pause
net stop dnscache
echo .*** START THE DNS CACHE ***
pause
net start dnscache
Or:

@echo off
echo .*** RUNNING IPCONFIG /FLUSHDNS ***
ipconfig /flushdns
echo .*** STOP THE DNS CACHE ***
start /wait net stop dnscache
echo .*** START THE DNS CACHE ***
pause
net start dnscache
That way no pauses, and start /wait forces the batch file to wait until the net stop dnscache finshes before trying to start it

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Commandline-ophobes can also right-click on the connection, either in the Network Connections control panel applet or in the taskbar (if you have it set to always display there), and choose "Repair".
In addition to flushing the DNS cache, this renews the DHCP lease, flushes the NETBIOS cache, and reregisters NetBIOS and IP address with WINS.
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Please post back if you have any more problems or questions.