On entry to ZGEBAL parameter number 3 had an illegal value

Obviously ZGEEV uses ZGEBAL. ZGEBAL parameter number 3 is the input matrix.

In my program I have to get the eigenvalues of a complex(8) hamiltonian matrix.

The issue disapears when I change some terms in my matrix.

Does that mean that my matrix is not diagonalizable, or is it another technical problem?

PS : I'm french, so excuse my language.