Cannot boot joyride-2200 from USB stick

[Ton van Overbeek]

Hello,

My xo-1 is currently on build 708.
For testing joyride-2200 I did not want to reflash yet, but boot from a 
USB stick instead.
So I downloaded the image from 
http://xs-dev.laptop.org/~cscott/xo-1/streams/joyride/build2200/devel_ext3/xo-1-olpc-stream-joyride-devel_ext3.img.bz2, 

unzipped it and copied it to a 1 GB Sandisk USB stick.
Booting with extended messages (X game key pressed) shows that OFW finds 
my developer key
in the main flash, finds the OS on the USB, does not update the firmware 
(no external power)
and then loads the ramdisk.

Booting starts, but mounting /dev/sda1 on /sysroot fails because the 
usbcore.ko module
needed by usb-storage.ko cannot be found.

Some of the messages are (copying manually from the xo-1 screen and 
skipping the stack depth messages):
--------------
FATAL: Error inserting usb-storage 
(/lib/modules/2.6.25-20080722.2.olpc.d86980aeb8d0adb/kernel/drivers/usb/storage/usb-storage.ko): 
Unknown symbol in module, or unknown parameter (see dmesg)
mount: mounting /dev/sda1 on /sysroot failed: No such device or address
Traceback (most recent call last):
  File "/init", line 131, in <module>
    lease_writer, run_init)
  File "/antitheft.py", line 31, in run
    return run_init_callback()
  File */init", line 103, in run_init
    root_mounted(xo, boothpath).__enter__() # hack to re-mount root
  File "/initutil.py", line 120, in __enter__
    check_call({'/bin/mount','-n','-o',access]+extra+[dev,'/sysroot'])
  File "/usr/lib/python2.5/subprocess.py", line 461, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['/bin/mount, '-n', '-o', 'ro', 
'/dev/sda1', '/sysroot']' returned non-zero exit status 255
----------------

Is this (booting from USB) supposed to work? Has it ever worked?
Or am I missing something?
It seems that usbcore.ko has to be available early in the boot, but 
cannot be found.

Any hints on how to proceed, or instructions on providing more data are 
appreciated.

Regards and hoping to be able to test joyride-2200 soon.

Ton van Overbeek