what happened with curse client

I ran and installed this but I can't log into the client. I can log into my-curse. I even logged in to post this. It just won't let me log onto the client, after a 5 sec countdown it says login failed. My husband's computer shares the same incoming internet account via Verizon fiber and he's able to use the client just fine. He thinks it could be an ip or dns problem. I'd appreciate your help. Thanks. :D

Mine always says (during installation) "Failed to update security settings for World of Warcraft mod installation folder. You will have to grant write on Interface/AddOns manually."

After that it doesn't even let me log in. I get some sort of "Illegal operation" message.

I got the same error as Micmak and for some reason when I try to dl an addon using the client it says something about not being able to write in a DoWrite file or something, and the addon never loads. Everything worked fine before 2.4 >.<