I've posted about this elsewhere on the forum too, because if anyone else is like me, they've scoured the web the past 24 hours for answers to this!
Do you have Spectrum? I have had the same problem since about 5pm yesterday. I spent hours troubleshooting, even submitted an SL support ticket (no response yet on that), and finally contacted Spectrum today.
Here's the response I got from Spectrum : "I do apologize for the inconvenience, but there is currently a known issue we've encountered regarding some game servers and certain websites, but our engineers are engaged and working diligently to resolve this as quickly as possible. We do appreciate your patience and understanding."
I did some research (entered this same response into Google) and came upon this at Elder Scroll's (another online game) forum: it's a "problem in Washington, Oregon, California, Nevada and Arizona ..." Yikes. I hope they resolve this soon. Especially when "Multiple customers are experiencing this issue." (Spectrum quote)
We all have important things to do inworld, right? I've got starving breedables, Lol. Poor little horsies.