[charlesdm]

Honestly, the only way to solve this is to be direct and ask him to leave the company. Bringing that up could go two ways; really good or really bad.

If he leaves then the company will probably have to buy back his equity stake, which will be expensive.

Also, don't forget, he probably has the power to fire you on the spot. These things do happen.

[jacquesm]

Nonsense. You don't crash a start-up on the say-so of an early hire.

A founder is a founder and barring actual misconduct or behavior that goes directly against the interest of the company should not be treated like he/she was a new hire, especially not by a new hire.