I've had ten days since one person has registered on my site normally i get 1,2,3 registrations a day and two people have emailed in that they reg but don;t get a password.
I can manually found that person in the users but they didn;t get sent out password and login instructions.
All this i have noticed since upgrading to MU was fine before for months on end.
I have got Login With Ajax plugin. Unistalled and reinstalled it but no go anything else i could try troubleshot?