Since people are having trouble logging into the Justin.tv (JTV) chat via IRC clients, I'll explain how I was able to log in via mIRC. I know that Grifforzer was able to do it in a different manner than this, but whatever works is fine!
Official Guide: http://www.justin.tv/p/irc_guide
mIRC is capable of connecting to multiple servers (i.e. Ustream and JTV) at the same time. Just open up multiple mIRC windows. Alternatively, you can go to File -> New Window to make multiple server tabs within the same window. Credit to Eat_Box for the tip!
For the most part, follow Foxtrot's tutorial with the following changes:Part 2:
Put your JTV username in the fieldsPart 4:
Make sure you put in your JTV passwordPart 11:
Either "thetombobblendershow" or "#thetombobblendershow" will work
After everything is finished, click the lightning bolt. You should get something similar to this:
If you're successful, then you'll immediately connect to the chat!
If you're still stuck, don't worry! Leave a post describing your problem and we'll see what we can do. Thanks for watching The TomBobBlender Show on JustinTV!
One more thing: If you start to see double posts, just restart mIRC. It happens occasionally.