Project naming, Sketch name prevents the Arduino Java app from starting.

This is a strange one, I just thought would be interesting to hear if others have experienced this.

I have a small sketch named 3ButtonFunct, when I click on the file, the Arduino IDE splash screen opens, then after 30-40 seconds a 'Launch4j' dialog box opens indicating: An error occurred while starting the application.

When I place an underscore before the 3 (_3ButtonFunct), the sketch opens quickly. I have not found any discussion about naming restrictions. I'll be testing this on a different PC.

Yes, a sketch name cannot start with a number. If you had tried to save that from the IDE it should have warned you.

The sketch name had to be modified. Sketch names can only consist
of ASCII characters and numbers (but cannot start with a number).
They should also be less less than 64 characters long.