Is this being seen on XP or Vista? Lately IE 7 has been seeing bugs there on Vista where turning off the DEP(data execution protection) cleared the sudden inability to log onto the home page while Vista's Wndows Mail(formerly Outllok Express) would open right up as usual.
For Vista to see this problem corrected with the latest updates on first open up the accessories>command prompt and type the following. "bcdedit/set nx AlwaysOff" like you see this here. You will see a confirmation when it is turned off at that time.