perfectbr@mail.com site defacement

A client's XP laptop using IE 6 and all updates installed, is opening to her website and gets the typical message left behind by Perfectbr after they deface certain websites (PerfectBr has.....at perfectbr@mail.com. Another box on the LAN, win98, is also seeing the same thing. When anyone else opens the site, including those outside of the LAN (my office network), nothing but what should be there is there - the correct site. I've searched for information and found that they deface websites, but this website hasn't been defaced. Just what the client sees when opening ONLY that web address on the local box in IE 6. Nothing comes up on antivirus - can't find anymore info. Can anyone help?