The way it works:

A connection is initiated. Then, via your Internet Service Providers (ISP) name resolution services, the IP Address/Hostname is resolved to a specific destination and your connection is routed accordingly.

It will travel over a specific route across the country passing through as many as 15-30 different routers. At any point in that chain, if a router is down or experiencing packet loss (data loss), it will cause a problem. Thus, it can give you the 'Page not Available' message when trying to log in or it will manifest as a loss in connection if you are currently logged in, or even manifest as a slow choppy connection.

Why can you still get to the Internet and E-mail? Simply because, in going out to other web pages, you will be traveling a different route and not hitting the same set of routers. Additionally, Citrix requires a very stable connection and has a low tolerance of packet loss, whereas general Internet usage has a very high tolerance of packet loss and will generally work fine on a poorer connection. Unfortunately, this does happen, and it is out of our/your control.

You can contact your ISP and ask them to check their lines, or you can ask your internal IT staff to run a 'tracert' to 208.111.140.51. This may help identify where the problem is.

Most of the time, these outages are limited and only last a few minutes before the provider whose router is having issues discovers the problem and rectifies the situation.

This is a rather common occurrence in the overall scheme of things when it comes to the Internet.