SSH without password - problems with particular userid

I'm using ssh (/bin/ssh) on Solaris 10. I can ssh between accounts
without a password with no problem for most accounts - i.e., I've
generated keys, set up authorized_keys files, set the appropriate
permissions on directories, etc. With one particular userid, though, I
still get prompted for a password. I've checked permissions, tried
dsa, rsa, etc. but still no luck.

Is there some account-specific configuration option somewhere that
dictates whether or not it is possible to ssh to a particular account
without a password?

Many thanks,...
Mike Dunham-Wilkie