I guess that either you've already figured it out by now or changed irc-client or something... but still, i felt like answering this when i saw it.
Ok, so i had the same problem, i could recieve via dcc, but i couldn't send. But then a person pointed out that maybe it was "that strange letter" that was the problem. And he was right! I had an "å" in the name of the folder where the thing i was sending was. So, i removed it and put an "a" instead, and it worked, i could send.
So, if you still haven't figured it out, of if somebody else is reading this and have the same problem:
Just check so there aren't any "strange letters"