Windows 7 User not able to login until reboot

[gemidriver]

We have a user who often of a morning when he goes to login the computer doesn't allow him, stating incorrect details.

if he reboots the computer, and tries to login again it works without a problem

here are logs from one of the domain controllers

can someone shed some light please

01/22 06:45:34 [MAILSLOT] [1272] Received ping from TAC8469((null)) domain.com.au. t2361 on UDP LDAP

01/22 06:45:34 [MAILSLOT] [1272] DOMAIN: Ping response 'Sam User Unknown Ex' t2361 to \\TAC8469 Site: TOMAGO001 on UDP LDAP

01/22 06:45:35 [MAILSLOT] [84] TAC_DOMAIN: Received 'Sam Logon' message on \Device\NetBT_Tcpip_{05F62CA1-D87F-48FE-9D92-E500BB3BF6B8}

01/22 06:45:35 [MAILSLOT] [84] TAC_DOMAIN: Ping response 'Sam User Unknown Ex'

01/22 06:45:41 [MAILSLOT] [84] TAC_DOMAIN: Received 'Sam Logon' message on \Device\NetBT_Tcpip_{05F62CA1-D87F-48FE-9D92-E500BB3BF6B8}

01/22 06:45:41 [MAILSLOT] [84] TAC_DOMAIN: Ping response 'Sam User Unknown Ex' t2361 to \\TAC8469 Site: TOMAGO001 on \Device\NetBT_Tcpip_{05F62CA1-D87F-48FE-9D92-E500BB3BF6B8}

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