Have no problem accessing www.navy.mil sites or history.navy.mil sites.
Are you running with a host file by chance? There has been an ip code change take place over the past few weeks going to the expanded ip numbers. That change over at my ISP gave me a few bumps for a day or so until the changeover was complete.
If you are using an old host file, many ip numbers are likely to be invalid.
How many digits have ip addresses expanded to?