Sometimes when I try to connect a server I'll get this weird error. It's usually different each time but it's stopping me from getting on any minecraft servers most of the time.
It sounds like a problem with the modded servers you are trying to join, contact the server/server owners about it to see if you are either missing mods needed to join the server or to see if there is an issue with the mods on the server.
Test your internet connection at http://speedtest.net/ and share the result here. Also, make sure you are using the same version of Minecraft as the servers you are trying to join.
Like this:
Also the results of speedtest: