Sorry for not replying sooner, but ive been snowed under!
Anway the problem you have does happen from time to time. As the error suggests, there are just too many people logging in to the server from which you access all the irc channels. Now there are lots of servers all around the world that provide access to irc. So if one's full then all you need to do is use another. Unfortunately not all servers welcome you with open arms. For example some US servers dont like us europeans or brits, depending on your euro-ness leanings, using their servers and won't let you in. Best to try servers which are geographically closest. And of course you change your server by going into options and choosing the server from the drop down menu.