Since upgrading to Lion, iChat refuses to connect to either my AIM or Google Talk accounts. (Not a Google Apps account, fwiw.) Interestingly, if I sign in to AIM on another computer and try to get iChat to sign on, I get a message that I'm trying to sign on in more than one place, but iChat still shows status as "offline" for all accounts.
So far, I've tried deleting all the com.apple.iChat preferences in Library, but to no avail.
Best Answer
For some reason iChat defaulted to selecting "https only" on aim and gtalk for me. Once I deselected both https options, iChat accounts connected successfully.