Thanks again, BDAqua.
Putting the problem sites' IP addresses directly into the browser doesn't make any difference, they still time out. By the way, are you running 10.4.11, and can you access those sites, adobe.com and support.lexmark.com?
The traceroute results are helpful :-
. from OS 10.5.8 to 'support.lexmark.com' (working in browser)
Traceroute has started ...
traceroute to support.lexmark.com (192.146.101.175), 64 hops max, 40 byte packets
1 192.168.2.1 (192.168.2.1) 10.709 ms 1.296 ms 11.103 ms
2 203.23.236.34 (203.23.236.34) 19.022 ms 21.922 ms 18.397 ms
3 core-syd-lns2.comcen.com.au (203.23.236.45) 19.279 ms 11.831 ms 16.595 ms
4 vlan551.22rrc76f000.optus.net.au (59.154.10.17) 115.309 ms 11.618 ms 35.038 ms
5 203.208.191.157 (203.208.191.157) 175.660 ms 174.232 ms 178.382 ms
6 67.17.192.141 (67.17.192.141) 180.202 ms 179.554 ms 190.632 ms
7 cw-gw.wswdc.ip.att.net (192.205.32.45) 186.321 ms 183.906 ms 177.638 ms
8 cr1.sffca.ip.att.net (12.122.200.10) 244.370 ms 250.120 ms 249.583 ms
9 cr1.cgcil.ip.att.net (12.122.4.122) 232.710 ms 250.847 ms 239.889 ms
10 cr81.ipsin.ip.att.net (12.122.152.137) 248.649 ms 248.965 ms 251.039 ms
11 12.122.152.169 (12.122.152.169) 278.113 ms 250.306 ms 259.287 ms
12 12.88.94.10 (12.88.94.10) 248.377 ms 249.069 ms 260.430 ms
13 * * *
14 * * *
. from OS 10.4.11 to a normal working site, 'apple.com'
Traceroute has started ...
traceroute: Warning: apple.com has multiple addresses; using 17.149.160.49
traceroute to apple.com (17.149.160.49), 64 hops max, 40 byte packets
1 192.168.2.1 (192.168.2.1) 6.791 ms 30.325 ms 29.338 ms
2 203.23.236.34 (203.23.236.34) 11.601 ms 11.064 ms 19.581 ms
3 core-syd-lns2.comcen.com.au (203.23.236.45) 23.240 ms 16.406 ms 16.618 ms
4 vlan551.22rrc76f000.optus.net.au (59.154.10.17) 23.686 ms 16.490 ms 16.650 ms
5 203.208.191.157 (203.208.191.157) 183.518 ms 172.550 ms 173.038 ms
6 xe-10-1-1.sjc10.ip4.tinet.net (216.221.157.157) 175.765 ms 171.659 ms 188.282 ms
7 4.68.62.213 (4.68.62.213) 182.833 ms 194.200 ms level3-10ge-peering (77.67.69.98) 184.416 ms
8 apple-compu.edge2.sanjose3.level3.net (4.53.210.46) 190.886 ms 185.874 ms 233.710 ms
9 * * *
10 * * *
.from OS 10.4.11 to a problem site, 'support.lexmark.com'
Traceroute has started ...
traceroute to support.lexmark.com (192.146.101.175), 64 hops max, 40 byte packets
1 * * *
2 * *traceroute: sendto: No route to host
traceroute: wrote support.lexmark.com 40 chars, ret=-1
*
traceroute: sendto: Host is down
3 traceroute: wrote support.lexmark.com 40 chars, ret=-1
*traceroute: sendto: Host is down
traceroute: wrote support.lexmark.com 40 chars, ret=-1
*traceroute: sendto: Host is down
traceroute: wrote support.lexmark.com 40 chars, ret=-1
*
4 * * *
So it seems that, for the problem sites, the correct IP address is obtained, but the attempts to contact the sites don't even get past my router, which has the internal address 192.168.2.1. Is this correct, and why would it happen consistently on only a few sites, when most sites work ok?
Thank you, Phil J