Looks to me like the problems you describe just might be related.
My suggestion would be to re-run vipw - assuming that's what
recreates /etc/pwd.db  (it has the exact date/time on my system
as /etc/passwd has).

My guess is that your /etc/pwd.db is corrupt somehow.  If email
is working to/from other users, that probably means sendmail
is running correctly in the background.  If it's not, that might
cause similar problems (but wouldn't explain why adding one new
user account broke another existing good one).

Let us know how you make out!

-- dick
_____ __//________________________________________________________________
R. H. \X/ood                                             dwood@rhw.pic.net
246 Bancroft Drive,     Garland,  TX   75040    USA        +1 214 530 2595