unable to move files from external usb disk
This might be a silly question but are you sure that the drive is mounted read-write.

From memory, if you type in "mount" in a Terminal it should tell you if the drive is mounted read-only as one of the properties in brackets after the drive. Or you could right-click the drive in the Finder and choose Get Info from the context menu and check "Sharing &amp; Permissions" at the bottom of the Info window. I think it'll tell you there if the drive is mounted read-only.