YaST problems

Greetings : I'm running SuSE 6.2 and am having some problems with YaST... if I add a user to my system, then try to send mail to that user, or su to that user, or do anything to that user, I get a 'User does not exist' error. HOWEVER, the user is listed in both the shadow and passwd files, belongs to a vaild group, has a mail spool and a home directory. I'm more that a little confused. :) Any help here would be greatly appreciated. Regards, Bryan Porter