Remote access isn't too hard to execute one a machine that doesn't have solid defenses. Either that or Morwen's statement about similar client build and account use. Lasa, use Morwen's link and check those IP logs ASAP. If you see an IP that isn't yours using Lasa right before your ban (especially if it's WAY the hell away from your physical location), then you have some evidence to help you.
The worst thing that could happen is they wonder whether you shared your account info with someone else, but I don't think they'd jump to conclusions like that, especially if the IP logs your access consistently from the same IP. Either way, it's action you can take now.