i shall say that both these roms are XWLA4 based, and i never ever experienced the same issue with every other rom i used before XWLA4 came out.
it just happens randomly; i installed the whole system, removed a few apps, installed a few others, used the phone for some days with various reboots and all was good.
all of a sudden, after booting there are no memory partitions mounted, none of them -internal and external-
doing a cache + dalvik cache wipe doesn't help; after wiping, system mounts memory partitions correctly but the following boot messes everything again.
flashed again siyah 2.6.11 and 2.6.12 - didn't help.
when booting in recovery, i can browse memory partitions without any problem, which leads me to exclude any hardware failure.
help needed, please.