I saw your thread and tried my hotmail. Mine is working fine, got in no problem.
Worth a try:
If you encounter a certificate errors at a website you have visited before without errors, it’s possible the website is not configured correctly. Try retyping the address you are using. For example, if you are typing the address as https://example.com, try changing it to https://www.example.com.
What addons do you have? Did you block something with adblock or noscript? I find if I adblock *everything* that I think is an ad, sometimes the page will hang or a link wont work until I fiddle with the adblock settings.
Also check your computers date.
There's your problem right there.
But seriesly, my sister-in-law reported having the same problem the other day. I'd recommend switching to Yahoo mail or Google mail.
Also might not be a bad idea to make sure no one is intercepting your internet communications. Though unlikely, that circumstance will create such an error.
are you logged in?