Whilst logged onto the iMac as a local user burning discs works fine. Whilst logged on as a windows network user (server 2003) burning fails. I presume this is a permission issue but the windows account is an administrative account for the domain so shouldn't have any restrictions from the windows side. I have, however, found that some software needs installed with the local Mac admin account to succeed and the windows user account shows in the Mac accounts panel as an Admin, Network, Managed account.
Any help appreciated.