Thinkpad T420s + Intel X25-M SSD Problem

[debris]

For some reason the 80GB X25-M I have won't work in AHCI mode. The BIOS won't detect the drive, and I can't access BIOS setup after changing from Compatibility to AHCI mode. After unplugging the SSD and changing back to Compatibility I can access BIOS setup and the disk is detected again.

In AHCI mode, Windows 7 install starts after a short wait and detects the drive, but says Windows cannot be installed:

The computer's hardware may not support booting to this disk. Ensure that the disk's controller is enabled in the computer's BIOS menu.

In Compatibility mode Windows installs ok, but trying to change to AHCI after install (after regedit), no dice.

This was the closest I could find on the Internet: http://forums.hardwarezone.com.sg/stora ... 82263.html, but obviously this has nothing to do with Windows 7 creating 0kb partitions.

The SSD has latest firmware. (EDIT: Also checked with Lenovo Solid State Drive firmware update utility)

Any clue?