Hello,
I don't know if I'll help...
what decoder is this?
For me on adb2850 it looks like this:
	 
 
clean uboot without -env
nBOX ADB28xx by plfreebox@gmail.com  [32-bit mode]
U-Boot 1.3.1 (Aug  5 2012 - 10:17:06) - stm24_0057
DRAM:  256 MiB
NOR:     4 MiB
NAND:   64 MiB
*** Warning - bad CRC, using default environment
In:    serial
Out:   serial
Err:   serial
adding env
set ethaddr 00:01:01:01:01:01
set bootdelay 3
set bootkern_0 'usb reset; ext2load usb 0:1 80060000 /boot/uImage; bootm 80060000'
set bootargs_0 'set bootargs console=ttyAS0,115200 root=/dev/sda1 rw mem=256m coprocessor_mem=4m@0x40000000,4m@0x40400000 rootdelay=6 nwhwconf=device:eth0,hwaddr:${ethaddr} init=/bin/devinit'
set bootkern_1 'nand read.i 0x80060000 0x0 0x300000; bootm 80060000'
set bootargs_1 'set bootargs console=ttyAS0,115200 root=/dev/mtdblock1 rw rootfstype=jffs2 mem=256m coprocessor_mem=4m@0x40000000,4m@0x40400000 nwhwconf=device:eth0,hwaddr:${ethaddr} init=/bin/devinit'
set bootcmd 'run bootargs_0; run bootkern_0;run bootargs_1; run bootkern_1'
saveenv
ledblink 3 0 200
and after uploading the env I have this
U-Boot 1.3.1 (Aug  5 2012 - 10:17:06) - stm24_0057
DRAM:  256 MiB
NOR:     4 MiB
NAND:   64 MiB
In:    serial
Out:   serial
Err:   serial
Hit any key to stop autoboot:  3  2  1  0 
(Re)start USB...
USB:   scanning bus for devices... 2 USB Device(s) found
       scanning bus for storage devices... 0 Storage Device(s) found
** Can't read from device 0 **
** Unable to use usb 0:1 for fatload **
(Re)start USB...
USB:   scanning bus for devices... 2 USB Device(s) found
       scanning bus for storage devices... 0 Storage Device(s) found
** Bad partition 1 **
## Booting image at 80060000 ...
maybe you also need to download the env appropriate for your decoder
	 
 
u-boot file for adb2850 I have..
did you ask from the source plfreebox@gmail.com?