What Game?
Anyone else using this account other than you?
Most online games such as from Blizzard Entertainment have memory sniffers. The memory sniffer looks for memory address manipulation of otherwise protected addresses that are the target of cheating, it will report back to them and they will ban you. If this was unexpected, I would be checking your system for any malware or virus's that are trying to lift information from your account. A dirty addon module etc in which a gold farmer or hacker is looking for you to type in information that will allow for them to gain control over your account and steal virtual property and wealth as a means to sell it to someone else on black market for real money.
More information is needed as Allan stated.
Generally you need to work out a ban with the game company, the first offense is usually a lock out period to teach a lesson that your system was caught and stop it. They dont permanently ban unless habitual offender or hacking took place in which you really blew it with them to where your too high of a risk to them to allow back in under that same account.
