Leo says this doesn't sound like it's actually ebay.com. It sounds like something on his system is hijacking his browser and sending him somewhere else. One way malware could do this is by changing his "Hosts" file. So when he visits ebay.com, his computer will check that modified "Hosts" file and send him somewhere else. He might also have DNS Changer on his system which would then change the lookup results he would get and send him to a phony DNS server.
Joe says that in the past day or so, the ebay site has been down for him entirely. This is most likely because the hacker was caught and the site was either taken down, or he took it down. But his computer is still trying to send him to that phony web address.
Leo says his system has been corrupted, and may be corrupted in other invisible ways that he may not like. Leo's presumption is that they may have done many other things too. He recommends doing a complete reformat and reinstall of Windows from a known good source. He should make sure to backup his files first, but not his programs because he could end up backing up the malware then too. If he doesn't want to do this himself, he should take it to a professional and encourage them to wipe it and reinstall Windows.