Those pages work for me. The sites might be blocking you, though I'll assume not as you've not indicated that you've done anything that would cause them to do so.
If it doesn't work in another browser (which you seem to suggest it doesn't in IE), I suggest you start with some simple diagnostics. Run the command prompt and use the "nslookup" and "ping" commands, with each address that doesn't work; you can post the results here for someone to comment on if you don't know how to interpret them. If you are having DNS or network issues that should help discount the obvious. If you don't know how to use
nslookup or
ping, read the help pages (linked). There are other tools such as "tracert" and "pathping", try those too if you can (again read the help pages if you don't know the exact command to type).