I had exactly the same problem a few months ago. I was unable to see the NI website nor Exchange from my workplace, but everything work fine from my home computer.
Check with your system administrator (Although, it can be hard to convince them that the problem is in the system they manage. In my case, my sysadmin keeps saying that maybe NI shutdown their site at certain hours
🙂 Unbelievable attitude!) As Shiner suspect, maybe they made some changes to the firewall or proxy settings that is affecting you.
www.vartortech.com