is your v3.x hangs related to this topic http://forum.mikrotik.com/t/very-strange-3-x-4-x-5-x-freeze-and-crash-with-pppoe/22670/1 ?
i know SATA is not supported in 2.9 but i have downgraded from 3.x to 2.9.51 with SATA and it worked fine. just remember to upload 2.9 packages to mikrotik and hit the downgrade . i did this way .