I am having a similar issue. I have a Win98 Desktop directly connected to an ADSL modem - SIEMENS Speetstream 4100. That connection works well.

I had a WRT54G (old school, blue and black) wireless router connected to it which allowed me to use my WinXP laptop in the house. I then upgraded the router to  a WRT54GS2, and now I lose the connection to the internet every minute or so while connected through that. The connection through the modem goes down, not the connection to either the desktop or the laptop. 

Here's the output of ipconfig /all when my laptop is connected directly through the ADSL modem:

Windows IP Configuration

        Host Name . . . . . . . . . . . . : ALIENUS_AES
        Primary Dns Suffix  . . . . . . . :
        Node Type . . . . . . . . . . . . : Broadcast
        IP Routing Enabled. . . . . . . . : No
        WINS Proxy Enabled. . . . . . . . : No

Ethernet adapter Local Area Connection:

        Connection-specific DNS Suffix  . :
        Description . . . . . . . . . . . : Realtek RTL8139/810x Family Fast Eth
ernet NIC
        Physical Address. . . . . . . . . : 00-0F-B0-74-0F-FB
        Dhcp Enabled. . . . . . . . . . . : Yes
        Autoconfiguration Enabled . . . . : Yes
        IP Address. . . . . . . . . . . . : 70.234.142.61
        Subnet Mask . . . . . . . . . . . : 255.255.255.0
        Default Gateway . . . . . . . . . : 70.234.142.62
        DHCP Server . . . . . . . . . . . : 192.168.0.1
        DNS Servers . . . . . . . . . . . : 192.168.0.1
                                            192.168.0.1
        Lease Obtained. . . . . . . . . . : Friday, November 20, 2009 1:23:03 PM

        Lease Expires . . . . . . . . . . : Friday, November 20, 2009 1:33:03 PM


Ethernet adapter Wireless Network Connection 2:

        Connection-specific DNS Suffix  . :
        Description . . . . . . . . . . . : Broadcom 802.11b/g WLAN
        Physical Address. . . . . . . . . : 00-90-4B-F3-5E-D6
        Dhcp Enabled. . . . . . . . . . . : Yes
        Autoconfiguration Enabled . . . . : Yes
        IP Address. . . . . . . . . . . . : 192.168.10.100
        Subnet Mask . . . . . . . . . . . : 255.255.255.0
        Default Gateway . . . . . . . . . : 192.168.10.1
        DHCP Server . . . . . . . . . . . : 192.168.10.1
        DNS Servers . . . . . . . . . . . : 192.168.0.1
        Lease Obtained. . . . . . . . . . : Friday, November 20, 2009 1:03:43 PM

        Lease Expires . . . . . . . . . . : Saturday, November 21, 2009 1:03:43
PM
 

Why does the new WRT54GS2 lose internet connectivity? Is it because I don't have Network Magic on the Win98 desktop? Is there anything I can do other than go back to my old router?

Thanks in advance.

I am having the same problem with my WRT54GS2 and my DSL modem. I have flashed the router

to the lastest flash.

Every 30 minutes or so I lose the connection between the router and the modem.  If I reboot

the router(repower) It comes back up again.

I don't see any way to copy and paste from the windows 7 cmd windows and here.

ie  ipconfig info