Active Directory Plug-In Logs

Dear Friends, We use the Active Directory plug-in to connect to a Windows Directory server from our 10.5 systems. This works well but one user can not log-in and is given a vague message to contact the system administrator. Here's what I want to know, where does the AD plug-in or subsystems keep access and error logs? I have looked and can't find them. I hope they will shed some light on things. Thanks!