The minimum password length is six characters. We will fix this in newer versions (i.e. to check the length.) A good idea is to just accept the default password.
BTW, my quick test on Redhat 6.6 worked ok. I was able to login as soon as opened up port 443 on the host.
I did see an error in the oxTrust log about "setCertificateExpiryAttributes" but I think that's a background process, not related to authn.