Check the filter levels on your firewall and AV.
If Win Xp:
Click Start / Run / type in; cmd
/ and at the black command screen type in; ipconfig /flushdns
Start / Run / type in; regsvr32 urlmon.dll
You might also try to empty your Temporary Internet Files folder:
Select Internet Options
Click the General
Click the Delete Files
When the box opens, put a check in Delete All Offline Content
Also check PC date and time.
Double click the time in the taskbar, to open, and make sure the Time Zone and Daylight Savings settings are also correct.
Some sites block access when you have incorrect time settings.
Also see if this is of any help:Error message: The page cannot be displayed