I attempted entering the Kaise123 server to find that I am locked out. It is not a bad internet connection as no "connection error" notification shows and I still have access to some other servers.
[spoiler]https://www.dropbox.com/s/1xp69vgx17dbmdr/Server%20connect%20issue.bmp (https://www.dropbox.com/s/1xp69vgx17dbmdr/Server%20connect%20issue.bmp)[/spoiler]
As that shows, only 1 server actually could not connect. I had full connection strength to the servers it lets me access, I just can't use Kaise123's server. :( I have checked the ban logs to see if I had been banned in my absence without my knowing, but my IGN did not show in any of the reports. I do not know what is causing this issue.
Your client is probably outdated. Notice the red 1.6.4 with the X?
If you're using the Kaisecraft client, when you open the client, hit new profile in the bottom left corner. Select version 1.6.4 in the one dropdown bracket in the menu that pops up, and rename the profile Minecraft 1.6.4. You should be able to connect then.
This has resolved the problem. Thank you very much ^_^