Can't Ping Router but have internet

This was a odd issue I have been working on, and I think it may be the cause of other issues. I am doing some tech work for a small office. There are 5 computers, a router, and a cable modem. Three of the computers are laptops that work wirelessly and are running XP Media Center. There is a desktop machine in the front of the office as well, wired, running XP Media Center. Finally, a Windows XP Pro computer is acting as a server for backingup files onto. The server also is wired into the router. Now everyone can connect to the router, Everyone has internet connection, and on a good day, everyone can connect to the files being shared on the server computer. None of the laptops can ping any other computer and can't ping the router, even though they are connected to it and have internet access. They also can't ping websites such as google.com, although it will resolve its IP before giving the usual Request Timed Out error. The desktop and server computer can't ping the laptops, but can ping eachother and everything else fine. I thought it may be an issue with the router and wireless settings, but I wired one of the laptops in and it couldn't ping anything still, except 127.0.0.1 Also, if I try to ping the server by name, I get: Ping request could not find host WealthWT. Please check the name and try again. When I tried to connect one of the laptops directly to the cable modem, instead of the router, I can't get internet at all on the laptop. This with unplugging and plugging the cable modem back in and running ipconfig /release and /renew. No internet connection, and still no pinging sites. When I wire the Xp Pro computer acting as the server, directly into the server, and after removing static IP and release and renew, I can get internet on the server. Only the server has static IP set, and it works fine with or without it set, it is static only because I was hoping it would make the connection from the laptops to the server more reliable. Also, none of the computers have Windows Firewall enabled.

Is the XP Pro Machine (file server) running a DHCP server? What are the ip ranges / subnet / DNS (have they all been checked? How long have you had the problem, did it happen over night? Sorry about all the question just want to get some details to make it more clear. Thanks Oh and does the router have a Firewall (correctly configured) and are the PC's using a firewall?

Ok, well, seeing as how I can't even connect to the internet when wired directly to the modem from two oft the laptops (only tested 2 of the 3) but if using a wired connection with wireless disabled, through the router, I can get internet fine, I was thinking the issue may be with the laptops, especially since the server and desktop in the front work fine and the server wired directly to the modem get internet fine. I was going to reset the router to factory defaults and reconfigure, but due to the issue above, I though there may be another issue. I do not have DHCP setup on the server, that is done through the router. Motorola WR850G. Also, all three laptops are the same age and model (purchased at the same time). I am unsure of when this started as I have only just noticed it. I know they have been having intermitent problems accessing files off a network share for several months now. Ip ran is 192.168.30.xxx pretty much 192.168.30.80 and up to 192.168.30.255 Subnet Mask is 255.255.255.0 on all, chechked to make sure they all had same subnet

Hello, I would like to ask about your firewall settings, and any other security applications that you have on the machines. Your fire wall may be set so that you can not ping (or that the machine may not be pinged) as this opens a hole for hackers.

The only possible firewall that may cause that in this situation, would have to be en-acted by the AV program installed on the computers. The Router doesn't have a specefic firewall setting to direct only at certain machines, and the desktops have no problem. I will take a look at the AV softwre.

I was refering to the firewall on the machines themselves. Windows firewall blocks the ping by default. You actually have to open the firewall and allow ICMP.(you need to allow incoming echo request.

Windows Firewall is turned off on all the machines

Also, none of the computers have Windows Firewall enabled.

I missed that.
Have you set up all of the machines on the same work group?
Normally I do not help some one who is doing this for profit, or as home work, but if you can share files, access the Internet, but can not ping I am wanting to see why.
What AV are you using?
This could be the router blocking the echo request, and the IP address set to the router (but should have changed when you renewed) have you tried wiring the laptops together with out the router?
What about the security settings in Internet options?

I've been out of the office for a few days, but am back today, so I appologize for the lack of activity. With the profit situation, if it makes you feel any better, the work I am doing is actually for my mother and father inlaw's office. ;-) Anyhow, I will look into the router to see if it is blocking echo requests but I don't remember seeing that option. Also, would explain why connecting the laptops directly to the Cable Modem would cause the laptops to no longer have internet connection.

Also, would explain why connecting the laptops directly to the Cable Modem would cause the laptops to no longer have internet connection.

If the machines are configured with a static IP address they would be trying to connect to the router's address, the modem would have a differant address.
Check Internet options to see if obtain an address automaticlly is checked, or if a static IP address is used.

Please read this fine article.

did not realize that the AV installed on these machines had their own Firewall (Trend-Micro). Seems like quite the sad little overlook on my part, but disabling this firewall has allowed ping requests to complete successfully. Thanks for your help! :-D