IE stopped working--any ideas?

I am using IE v.6.0 on a Win2000 laptop. I took it to Barbados for two weeks and once hooked it up to a LAN there. When I got back, IE could not find any address. I get the message, for any web site, that, “The page cannot be found”. In addition, the title bar of IE’s window says, “HTTP 404 Not Found” and the same message appears inside the window. Fortunately, I also have Mozilla on the computer and it runs fine. However, there are certain windows that Mozilla does not display. An example of that happens when I use Google to read newsgroups and the window you open to make a reply is not displayed by Mozilla and this has happened in other cases as well. I did not have this problem with Netscape 4.7, so it is not simply the use of IE only code.

Although I don’t think it relevant, I am using a DSL connection on my home network and no other program seems to affected.

Any suggestions would be appreciated.

While I am mentionng IE problems, I will mention one more. I frequently download files with extension .tex. The default for IE is to turn it into an .htm file and completely screw up the content. I can avoid that by choosing to download it as a .txt file, but it renames it as name_tex.txt and I have the bother of changing the name back. I could not find any way of adding .tex or other extensions to the list of recognized extensions. Is there any way of getting IE to recognize more extensions?