Second SATA drive stopped working (after lion upgrade)
Have you updated your EFI?  Lots of potential problems depending on the drive and the model of MacBook.

In particular it appears that SATA 3.0 drives (6.0 Gbps) are not well supported. The EFI update resolves some problems, but not others. Is the read only drive in the optical bay? That would be consistent with the kind of problems reported.