Well, ubiboot could find & load the kernels OK, that's clear from the log. Next step is the kexec() after which it is the 2nd stage kernel that is in charge of things, not ubiboot any longer. Usually when the kernel loads OK but fails to boot there are 2 possible easy faults (and some more difficult) The easy ones are, either something wrong with modules, or something wrong with init. Assuming you have booted the same kernels before with earlier version of ubiboot, then the modules must be correct. Can you check from your ubibot.conf that the preinit for harmattan is correct? It should propably be: G_OS2_INITSCRIPT="\/sbin\/preinit_harmattan" And check that you have /sbin/preinit_harmattan there and that it is executable. (BTW, did you change your preinit or are you using the same as before?)
# ls -l sbin/preinit* -rwxr-xr-x 1 root root 10661 Set 7 2011 sbin/preinit -rw-r--r-- 1 1010 1010 10661 Out 4 01:25 sbin/preinit_harmattan -rwxr-xr-x 1 1010 5001 5752 Fev 28 2013 sbin/preinit_nitdroid