Can you check the versions of the IE used in both the systems.
You need to reset IE back to factory settings here's how
In the menu Bar (if your menu bar is missing right click on the tool bar near the Home icon on iE7)
click on internet tools, advanced option.....and at the bottom you will see RESET INTERNET EXPLORER .
Go ahead and hit that button and your misery (hopefully) will end.
Joined: Aug 25, 2009
It was because of LAN settings (proxy settings) and changes at network domain level happened over night.
Finally we figured out it and changed users proxy settings ans it's working on his machine too..