This is called a false-positive and usually happens when an anti-virus company updates their virus definition files without checking them properly. The result is that the anti-virus software starts incorrectly detecting some applications as trojans or viruses. Unfortunately this happens all the time. For example, some time ago Microsoft Security Essentials detected the
Google Chrome web browser as a trojan and recommended that users delete it.
You would need to contact your anti-virus software company to report the issue and to ask them for a solution. They should then correct the error in the next update of their virus definition files and should be able to tell you how to prevent their software from behaving this way in the meantime.
