Well, for whatever reason, that network doesn't want users using 6.10 and they banned you for it. Such bans generally last 24-48 hours and then you'd be able to get back on with another version of mIRC. I don't think that was a smart thing for them to do, but it's their call what to ban on.
As for the errors, I'm not sure. I'd see if anything has changed recently on your computer (new software or something, maybe) in case that's the cause. Other than that, you might try a Restore Point from before it stopped working as that may fix the problem.
You mentioned scanning with antivirus software. I'd also recommend scanning with anti-spyware software such as Spybot: Searh & Destroy or Ad-Aware just to be on the safe side.
