I'm pretty sure it's your network connection that it's causing that behavior. Possible causes might be:
- from your ISP:
- routing problems;
- proxy servers;
- dns issues;
- on your home network:
- your router(s) might have a messed up config, caused by any of the previous reasons
I don't think that it is the setup on any of your devices, since it would be too much of a coincidence to have 3 devices with the same setup mistakes (unless you previously had to done that in order to work with a previous ISP/Internet connection). Besides, as you stated, they work fine on 3G.
A good test you can perform, would be to check with Network Utility (/Applications/Utilities/Network Utility.app) and check for Lookup (DNS) and Traceroute tests. Check Lookup and Traceroute info for www.youtube.com and www.google.com, something like this (these results are ofc from my connection, yours will be slightly different):
Traceroute has started ...
traceroute: Warning: www.google.com has multiple addresses; using 173.194.66.106
traceroute to www.l.google.com (173.194.66.106), 64 hops max, 40 byte packets
1 192.168.1.1 (192.168.1.1) 2.764 ms 1.253 ms 1.168 ms
2 * * *
3 bl3-73-49.dsl.telepac.pt (213.13.73.49) 14.024 ms 11.705 ms 10.031 ms <--- this means the request has passed through my network, and it is already on my ISP servers
Lookup has started ...
; <<>> DiG 9.3.6-APPLE-P2 <<>> www.youtube.com
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 17629
;; flags: qr rd ra; QUERY: 1, ANSWER: 5, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;www.youtube.com. IN A
;; ANSWER SECTION:
www.youtube.com. 83551 IN CNAME youtube-ui.l.google.com.
youtube-ui.l.google.com. 169 IN A 173.194.66.190
youtube-ui.l.google.com. 169 IN A 173.194.66.136
youtube-ui.l.google.com. 169 IN A 173.194.66.91
youtube-ui.l.google.com. 169 IN A 173.194.66.93
;; Query time: 47 msec
;; SERVER: 194.65.100.117#53(194.65.100.117)
;; WHEN: Fri Mar 30 13:31:20 2012
;; MSG SIZE rcvd: 131
One more thing: you mentioned using the devices through Wi-fi and 3G, but what about ethernet cable? same thing? Because it can be a wi-fi performace issue, although that would not explain why you are being redirected to a chinese server.