[WRT54G] Random connection drops on hardwired computer but not wireless connections

Question

I bought a WRT54G, it's a version 6 if that matters, using the latest Linksys firmware.
The WRT54G is connected to my main desktop and DSL modem, dynamic IP and PPPoE. I set the router with a static IP, there's WPA2 going as well.
I have a notebook and another desktop computer connected wirelessly.
The issue is that my main computer will seem to lose its Internet connection randomly for 15 minutes and then come back by itself.
The problem is hard to describe but I'll try:
Let's say everything is working fine, I go on www.someforum.com/forums and browse around then I go to www.bestbuy.com and click a few links.
Then the issue starts, I get a "Cannot find server" to sites I haven't visited yet in this session like Google or eBay. I can't ping them either. However, if I go to Best Buy or here, it still works fine. I can still browse the forums. So, it seems like somehow, if the connection is "cached," everything still works but I can't make new connections.
Also, during that 15 minutes when my hardwired desktop has the problem, my 2 other computers work fine over wireless.
I can access my router at 192.168.1.1 at all times.

Answer 1

Using the 2 procedures that you noted (answer ID 688 and 534) will get you port forwarding to a computer at a fixed LAN IP address behind your router.  This means that your desktop computer would have a fixed LAN IP address that is set in the computer itself, and not assigned by the router's DHCP server.  It sounds like the DHCP server is giving addresses to your other computers.
It is important to know what fixed LAN IP address you have assigned your desktop computer.  The reason for this is that Linksys has specific rules about assigning fixed LAN IP addresses, and if you don't follow those rules, you can get problems like the one you originally described.  That is the reason that I have pursued this question.
When you assign a fixed LAN IP address, it must follow these rules:
1)  Any fixed LAN IP address must be outside the DHCP server range, which is typically 192.168.1.100 thru 192.168.1.149
2)  The fixed LAN IP address must be consistant with the default gateway address, that is it must typically be in the form of 192.168.1.x
3)  The "x" in item 2 cannot be equal to 1 or 255
So typically, a fixed LAN IP address must be in the range of:
192.168.1.2     thru 192.168.1.99   or
192.168.1.150 thru 192.168.1.254
assuming that you did not change your default DHCP server range.
So for example, if you assigned your desktop computer an address of 192.168.1.101, this could be the cause for your problem.  So what address did you assign to your desktop computer when you used the Answer ID 534 procedure?