USB SOLUTION:
From 
http://tech.canterburyschool.org/tech/UbuntuWorkstationsLogins validated by the Windows server won't correctly pickup membership in local groups, making sound, USB devices, etc. inaccessible. To fix that do the following (Thanks to Steve Towson, Marist Brothers International School, Japan):
   1.  edit /etc/pam.d/gdm to include 
auth optional pam_group.so                       2.  edit /etc/security/group.conf to include 
gdm;*;*;Al0000-2400;floppy,audio,cdrom,video,plugdev,scanner                   Explanation:
   No.1 instructs gdm to use the /etc/security/group.conf
   No.2 assigns membership of the floppy, audio, cdrom, video, plugdev (usb sticks) and scanner groups to any user who logs in through the gdm.