On Saturday, I got one of the new 13″ MacBook Pro. I switched the 320 GB hard drive from my old MacBook with the 120 GB drive it came with. It took a trip to Fry’s and some frustration since the guts are not as accessible on the old MacBook. Everything worked great once it was finished and OS X reinstalled with new drivers.
Then yesterday, Apple released a [firmware update](http://support.apple.com/kb/HT3561) that added SATA 3 Gbps support from the crippled SATA 1.5 Gbps it shipped with. After updating, my new Mac has been randomly freezing when reading from the hard drive. My guess is the problem is an incompatibility with the SATA 3 Gbps between the drive and controller. Some stories mentioned that the SATA 3 Gbps support was originally disabled because of intermittent data errors.
I [posted in the Apple forums](http://discussions.apple.com/message.jspa?messageID=9695759#9695759) and it sounds like quite a few people who have upgraded the hard drive are having this problem. Unfortunately, there is no way to revert the firmware update. It might be possible to use the [WD Data Lifeguard](http://support.wdc.com/product/download.asp?groupid=702&sid=53&lang=en) tools to disable SATA 3 Gbps support on the drive. Unfortunately, the tools only work on Windows or DOS CD or floppy. The other option is to switch back to the original drive.