You BIOS doesn't support the "boot next device command".
If I am right, the "boot next device command" sends the value of "-1" back to the BIOS (= Device not found). Then the BIOS tries to boot the next device.
You can use the chain.c32 module instead.
* Chainload a hard disk (currently rather braindead.)
* Usage: chain hd<disk#> [<partition>] [options]
* chain fd<disk#> [options]
* chain mbr:<id> [<partition>] [options]
* chain boot [<partition>] [options]
* ... e.g. "chain hd0 1" will boot the first partition on the first hard
* The mbr: syntax means search all the hard disks until one with a
* specific MBR serial number (bytes 440-443) is found.
* Partitions 1-4 are primary, 5+ logical, 0 = boot MBR (default.)
* loads the file <loader> **from the SYSLINUX filesystem**
* instead of loading the boot sector.
* loads at and jumps to <seg>:0000 instead of 0000:7C00.
* equivalent to -seg 0x2000 -file <loader>, used with WinNT's loaders
* equivalent to -seg 0x60 -file <loader>, used with FreeDOS kernel.sys.
* equivalent to -seg 0x70 -file <loader>, used with DOS' io.sys.
* if the disk is not fd0/hd0, install a BIOS stub which swaps
* the drive numbers.
* change type of primary partitions with IDs 01, 04, 06, 07,
* 0b, 0c, or 0e to 1x, except for the selected partition, which
* is converted the other way.