Im having problems with Opera browser with loading certain sites.

While sniffing with Ethereal, I get a very very high count of "TCP Dup
ACK" (and I mean a VERY HIGH count, the loading of Slashdot have more
than 45k of it).

Im pasting two lines of the log, if anyone can explain whats happening
Im very grateful. (I cant paste the entire log here, its VERY long. But
i can compress and upload it somewhere)

46488 161.837312 10.0.0.2 66.35.250.55 TCP
[TCP Dup ACK 258#23057] 1209 > http [ACK] Seq=1313 Ack=3837 Win=32464
Len=0
46489 161.843931 66.35.250.55 10.0.0.2 TCP
[TCP Dup ACK 299#23047] http > 1209 [ACK] Seq=1662 Ack=1312 Win=16384
Len=0

ps. I received DupAcks for about 3 minutes with non-stop bandwidth of
8kb/s
ps2. That happens in Linux also, but the log was captured in Windows
ps3. It only happens with Opera.. Firefox and IE is everything ok
ps4. Im not behind a firewall or something. My router is fully open to
internet access

Thanks in advance,
Hugo