Mmm... okay, so it's not just a version difference.

How about you and Stu compare chip labeling -- what exactly is written on the top of the chip you installed? Stu, does that match yours?

The kernel does this: version = (version & 0xe7)
so the "c7" could really be "d7", for whatever that's worth.

But with it affecting the hard drive controller still.. Can you locate the power pins for the chip and measure the operating voltage on them?

Cheers