Windows Defender: "The program can't check for definition updates"

I installed Windows Defender, but it won't check for security definition
updates. Instead, I get the following error message: "The program can't
check for definition updates", with an error code of 0x800703e6. It may not
be coincidental that my Windows XP SP2 cannot connect with the Windows Update
site. Instead, I get the following error message:
"Error number: 0x80070715]
The website has encountered a problem and cannot display the page you are
trying to view. The options provided below might help you solve the problem."
I know that my internet connection is good (otherwise, I wouldn't be able to
send this question). I've reviewed several threads seemingly related to my
problem, but none of them seems to address it exactly, nor provide workable
solutions.

Please, I desperately need help solving the above two issues.

--
Gratefully,
Mr. Nudibranch

Go here: http://www.microsoft.com/security/portal/default.aspx

Under 'Latest Definition Updates', click the " 32 bit " link under
Windows Defender
SAVE the download to the Desktop
After it completes, double click mpas-fe.exe and that will install
today's definitions.

MowGreen [MVP 2003-2007]
===============
*-343-* FDNY
Never Forgotten
===============

I am getting the same error number on Defender, Windows Update and MS Update.
Thanks for the work-around for Defender and I can grab updates manually - the
error is browser-independent and only started in the past few months, after
an update. I was concerned that it was from spyware but I tried several
checking programs and found nothing. The KB has nothing on this error. Is
there a faulty DLL or some routine that needs replacing?
--
Ron