I have benn doing alot of buying and selling on E-bay lately.
Recently, when I try to go to the E-bay website, my browser says that
it is unavailable. I cannot acces MyEbay or the Ebay home page. My
friend went to his computer and logged into E-bay just fine with my
user name and password. I can go to any site on the web that does not
involve ebay. What is wrong with my system? I run Windows XP.

It may be your ISP, check with them.

I had a problem getting onto an important site (not ebay) that had
hitherto been OK.

My ISP gave me a different 'address' that I could use, on a different proxy server.

This worked and it's now nice to have the possibility of switching.

Worth checking.

Are you accessing ebay from a work computer? Many employers block ebay
these days so people don't shop during work hours.

Have you done anything on ebay that would have caused them to block
your IP address?

Have you tried accessing ebay with another browser, like firefox, if
you usually use internet explorer? This would eliminate the particular
browser from the equation.

Could a program you installed have changed your hosts file? Check your
hosts file using notepad. Open notepad, navigate to your windows
directory then system32 subfolder then usually the etc subfolder under
that. Tell it to look at all files and open file called hosts (no file
extension). Make sure there is no entry pointing ebay to your
localhost or someplace else weird (which won't work). If you find an
entry here you will have to remove it then save the hosts file.