I have recently switched ISP's and since I moved to my new ISP, when I try to connect to an IRC server, it will connect, but I can't use any commands, can't join any channels, and then it times out with "Software caused connection abort" or something like that. I called my ISP and they said they don't block any ports, it's not my firewall because it worked just fine before I switched ISPs and my setup hasn't changed. Anybody have any ideas? I can connect through mibbit.com just fine.

There is a large sticky in regards to "Software caused connection abort", however, since you didn't have this problem with your previous provider and your provider is the ONLY thing that you have changed, then the problem (to my knowledge) must be with the provider.

I know you said that they said they don't block, but experience has shown me that most of the people at the first level of help when you call an ISP actually have no idea about IRC or port blocking. You may need to call them back, then when you get to the first level help, ask for a supervisor or a more experienced technician.