eigs for complex sparse matrix eigenvalue problem

Hello, I am interested in solving an eigenvalue problem with a complex non symmetric sparse matrix and I am interested in the eigenvalue with the maximum real part. I used the command eigs with the option sigma='lr', but I obtain an error message saying that ARPACK routine zneupd cannot find a solution. Is there something I can try to get a solution without using the full matrix solver eig? Thank you very much!!!

[Teja Muppirala]

I probably don't have an answer for you, but just out of curiousity, how big and how many nonzero entries are in your matrix?