THIS POST IS DIRECTED MOSTLY AT LAN USERS BUT SHOULD ALSO BE OK WITH NORMAL DIAL-UP/DSL
We have recently had the same sort of problem at work,
aproximately 90% of the computers suddenly could not access the Hotmail website through internet explorer or were able to log onto the MSN Messenger service, error codes in MSN Messenger pointed to there not even being a connection to the internet, which was untrue, all remote, terminal services connections and website access to any other site that we could think of were still present..(the other 10% worked perfectly - the reason for this is the 10% of computers were used by employees who left at an earlier time than the other 90%)
now im not sayin that this will help everybody, but even if it justs helps the minority then this post has served its purpose.
i found the problem lay actually with our DNS server...
these were my steps of sorting the problem
i simply changed the dns server to a public dns server (4.2.2.1 - a new public dns server in america)
then;
Start | Run | type: CMD
when the command prompt is open type: ipconfig /flushdns
this will flush whatever dns information your computer has recorded so that the next time you try to access hotmail it will use the new dns server (4.2.2.1)to find hotmail .. it worked for me and hopefully will work for you.