Since you can surf the web without problem, and, it seems, that this has just started since going to your mom's place, from your dad's, it's possible that the ISP that your mom uses has a severe IRC blocking configuration, in that, it doesn't just block the IRC connection, but completely drops the internet.
You should have your mom check with her ISP, as she's their customer.
There may be other possibilities, but that's the first one I can think of.
