Quick Answer: This is caused by the system date and time on your computer changing at frequent intervals. It may be may be related your CMOS battery not working properly.
[Update, 13 Oct 2017: A new license management system is used as per today, which renders the Nalpeiron license manager as obsolete. Fill in your customer data in this form for us to provide you with the latest software build - http://re-compose.com/activate-your-license-for-liquid-notes.html ]
Expiration date bypass attempted messageLiquid Notes is equipped with a license manager that is part of the installation package of our software. It controls trial period, activation and deactivation of licenses, and ensures protection against piracy.
As such, the license manager sits deep in your system, monitoring any changes to the system time and date to prevent back dating for infinite extension of the trial period. If a change of system date and time is detected which is not in line with normal behavior, an error message "expiration date bypass attempted" is shown:
This may be caused by a problem with your CMOS battery, which is responsible to power your computer's main board so it doesn't forget the time. If the battery is weak, or not operating anymore, the system date and time will change to a date in the past, causing the license manager to present the above error message.