the credential supplied conflict with a existing set of credential

[scritch at altern.org]

i ve this pb only while  i tried to connect a another share with another user from the same  machine

FROM MACHINE ( client ) BETA ( NT4 WORKSTATION ) to samba's SHARES 

1/first connect as person 1 to share 1 = WORK
2/second connect as person 2 to share 2 = doesnt WORK 
the credential supplied conflict with a existing set  of  credential