IE7 Javascript problem

I’ve started having a problem with javascript enabled web sites like Dell.com and CBS.com. When I go to a site like Dell.com the top part of the page that has links to other parts of the web site does not show. I also get an error at the bottom left that displays this error when clicked on; Line: 2648 Char:4 Error: Class not defined Code:0. I have uninstalled IE7 and the page works fine in IE6 so I reinstalled IE7 only to have the same problem. I have uninstalled and reinstalled the latest version of Java 6.
Any suggestions would be appreciated.