My partner's dad just e-mailed me with the same problem. He is trying to access Hotmail from a Dell new laptop and can not but can access every other website he wants to. When he tries an older Toshiba laptop it works fine.
A colleague of mine also can no longer access Hotmail through the web but is okay on Outlook.
Has Hotmail published any advisories regarding incompatibility with certain computers? Any advice for what to do - would the Dell helpline be able to help as it seems their computer is the problem??