Comment 1 for bug 516150

I haven't used this particular package -- but I know from experience that disks can only have 4 *primary* partitions, of which one can be an *extended* partition in which you can create as many secondary partitions as you like. Maybe the same rules apply for virtual disks too?
See: http://en.wikipedia.org/wiki/Disk_partitioning#PC_BIOS_partition_types