Account registered but isn't on forum

[Fzerowii]

a friend of mine regestired on my forum but he isn't on the member list/when i click his profile it says invalid address. I though it was probably because he didn't active the account yet, but it didn't do that before when other members did the same thing. And the same thing happend to another member, i just had to go in and say activate his account...
so whyis this?

[Kalliopi]

I go and check mine ever other day or so, lots of threads on the subject, like this one here, but there is not a problem apparently.