I have a x25-m G2 in a Fujitsu-Siemmens Xa3530 laptop with the same problem that you. I think it´s a intel issue
As far as I know, when changing to AHCI mode in BIOS, you should always reinstall your OS. I got the same error as you when trying to change mode without reinstalling my os.
But then everything worked fine after reinstalling. Ofcourse you have to change it in BIOS THEN reinstall not reinstall first..
That's exactly the behavoir I got after flashing my SSD to 02HA.
Slow booting / freezing in every PC in AHCI mode.
And IDE works for a few minutes then it fails to recognize the SSD completely.
Do you run the latest (buggy) firmware 02HA, too?
Let's just hope Intel manages to bring out a bug fix to repair those SSDs without the need to RMA them...