Things you have tried and check:
1. Firewall is not blocking it.
2. Spy Sweeper not blocking.
3. Reset to default setting in browser.
4. Java, ActiveX.
5. Switch off router (you did for a long time).
6. Did you check your host file for "127.0.0.1
www.ssa.gov"
7. Did you try connecting to the site using the proxy sittings in IE or using a proxy site (myproxy) from google.
8. Did you try another DNS server as stated in Reply #12.
9. Did you try - Start-->Run and type cmd. Then type ipconfig /flushdns as in Reply #13.
10.Did you try Dropping the www or connecting to it from google (ssa.gov).
11. You have not been banned from the site.
Can you connect to the site using your network and a friends laptop ?
Go to
http://support.dlink.com/chooseCountry.asp find your make/model from "quick Link" top right.