Okay, from the log I can see that the last 2 times you loaded Harmattan the kernel was found correctly. (before that I guess you had a name or location problem since ubiboot did not find the zImage_2.6.32.54-openmode_l2fix kernel.

Now, as kernel is found but refuses to boot there are several possibilities.
Most often this is caused by problem in your preinit, and rare occasions it is mixup in the kernel modules.

Did you install the preinits.tar which contains preinit files for Harmattan, Nitdroid and Firefox?
If you did, can you check if the preinit files in /sbin/ have execute permissions?
If you did not, you should install the preinits.
If you do not have Nitdroid or FirefoxOS on your device, there's a quick hack you can do; Just copy the existing Harmattan preinit to a new name;

cp /sbin/preinit /sbin/preinit_harmattan

(of course you can also change the preinit name in your ubiboot.conf but for consistency's sake I'd like to use the postfixed preinits with ubiboot...)