Status 90 on drive paths listed on exclusion list

Running Netbackup Appliances on 2.6.0.3.

Having an issue where a couple of our backup clients, configured with policies that specify the ALL_LOCAL_DRIVES directive, but Exclude lists that list C:\ and S:\.  The only affected clients are configured as FT clients.  When the backups run, child jobs are created for all drives, including the c:\ and s:\ drives.  These jobs eventually fail with "(90) media manager received no data for backup image".

Has anyone come across this before or have any suggestions?