Took it back home. Plugged everything in. Started it up. The "can't connect to ANYTHING AT ALL" problem has been fixed. The IRC problem has NOT. Tried upgrading mIRC. That didn't work. Same problem as before: I apparently connect to the IRC server just fine, and if anybody types anything right after I join, I can see it. But then everything freezes up. No text from other people, no ping responses.
I guess I'll try calling the guy tomorrow and see if I can get him to make another house call.
Sick of this shit.