Why is DSLwireless is fast, but eth-wired slow

[joe at actionline.com]

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First, the background: 

One problem has led to another and another as I have been trying 
for three weeks to get my system rebuilt after it "crashed". 
I am preparing a "how-to" to recap everything I've needed to do 
to get everything put back together and working again, but I now have 
a new problem that I need to get fixed before I continue rebuilding. 

Thanks to an incredible amount of excellent (and very patient) help 
especially from Eric Shubes and from several other PLUG friends, 
I now have a fresh new installation of Mandriva 2006 working on a 
new 100-gig hard disk.  (Please, no comments about Mandriva as it 
is the *only* distro on which I can get Win4Lin to work with win98 
which is essential for my work.) 

We finally got Qwest DSL working via a new 2Wire modem/router. 
When booting my main desktop computer (eth-wire-connected) with 
a Knoppix live CD, the DSL connection works fine and fast.  And, 
with my dual-boot laptop, I have a good (54-Mbps) wireless 
connection when booting with WinXP.  I have not yet been able 
to get a wireless connection when booted with my Linux partition. 

Now the problem: 

When I boot up the new Mandriva installation on the hard disk 
(instead of booting the Knoppix CD), I have a DHCP Internet 
connection, but it is slower than molasses.  (I have not yet 
installed Win4Lin, so that is not a factor.)  As an example, 
when I connect either via wireless on the laptop or via Knoppix 
live CD on the desktop, and access usatoday.com, their website 
pops up in 3 seconds.  When I access the same website with my 
desktop box with the new Mandriva installation, it takes more 
than 30 seconds before the first page begins to appear and a 
total of 45 seconds before it finishes loading. 

I called 2Wire (excellent technical support) and they thoroughly 
checked everything and informed me that everything in the physical 
connection is fine, the modem is fine, and the Qwest connection is 
okay (just a few errors, "usual" for Qwest).  They also said that 
both browsers I am using are fine (Firefox and Konqueror), so the 
problem definitely has to be with my system's software --  perhaps 
something in configuration, a firewall, perhaps proxy settings, 
or some interferring program.

How can I resolve this? 

joe at actionline.com