Main ISP modem/router: 192.168.15.1, hosts the DHCP server for the whole network
Wireless router being used as an access point: 192.168.15.4, connected to the main (...1) router via its LAN port, with DHCP disabled
Computer A connected via LAN to the wireless router
Computer B connected via Wi-Fi to the wireless router
Wired router being used as a switch: 192.168.15.2, connected to the wireless (...4) AP, again all through LAN ports with DHCP disabled
Wired router also being used as a switch: 192.168.15.3, connected to the other switch (...2), ditto
Computers X connected to either the .3 or the .4 switch
(So the routers are daisy-chained 1..4..2..3 - sorry about them being out of order.)
All the computers are Windows XP or Windows 7 and almost surely don't have any weird configuration changes compared to when they were new and out-of-the-box.
The affected computers have websites that get "stuck" loading - the symptoms are as if the computers intermittently disconnect. To diagnose things, I have been running pings with lots of large packets, like "ping 192.168.15.1 -t -l 256 -w 100". The problem shows up only very intermittently if I ping using the default 32-byte packets.
Computer A is able to ping all the routers and the Internet without significant packet loss. Ditto for computer B.
Computer X suffers very high packet loss (about 35% dropped) to all the routers (including the switch it is directly connected to) and to servers on the Internet.
I can't figure out why A is able to ping fine to both switches, but computers connected to the switches cannot ping back out reliably. The computer that can't ping the switch it's connected to is really bizarre. I also am puzzled about what would make small packets okay but large packets not - line noise? Miswires? Collisions?
 It seems that not all the computers on the switches have this problem...still trying to figure out what the pattern is.
[edit2] And now one computer connected via Wi-Fi is having the same problems, but not the others that are via Wi-Fi; this is too weird. :/
[edit3] I think the Wi-Fi thing may be a different problem...disregard for now, I suppose.
Any suggestions for directions or additional diagnostics at this point?
Edited by AySz88, 12 March 2011 - 05:18 PM.