I just bought a brand new Sandisk 256GB Ultra Plus with latest firmware (X211200). I had the same very problem you guys have.
I followed instructions in this thread and managed to disable HIPM/DIPM by installing the .reg file and setting “Active” in all power profiles, as described in this thread:
http://www.sevenforums.com/tutorials/177819-ahci-link-power-management-enable-hipm-dipm.html
I have a Samsung NC110 (NP-NC110).
I hope this helps. Anyway, this is the last time I buy a Sandisk product, at least until they manage to release updated firmwares for their products.
