If you own a Unibody MacBook Pro and plan to upgrade the internal hard drive of the machine, then Apple’s Discussion Forums are warning of a serious issue which could affect you, a faithful 9to5mac commenter has reported.

The problem first surfaced in June this year, and continues to vex users today, if the 1,067 posts across 72-pages describing the situation are to be believed.

Apple introduced its EFI Firmware 1.7 update in June. The company’s tech note states this: “Addresses an issue reported by a small number of customers using drives based on the SATA 3Gbps specification with the June 2009 MacBook Pro.  While this update allows drives to use transfer rates greater than 1.5Gbps, Apple has not qualified or offered these drives for Mac notebooks and their use is unsupported.”

While most Mac users have reported no problems subsequent to installing the firmward update, others installing SATA II drives have experienced inexplicable crashes, system freezes and a variety of other problems. Some report that the system fails to recognise the newly-installed third-party hard drive when attempting to install Mac OS X.

Apple tech support have clearly been alerted to this issue, with Genius Bar operatives using tools to reinstall a previous firmware version, which has been described as fixing the problem. Another solution which some have claimed success with is to run an archive-and-install of  Mac OS X 10.5.8, but even here some customers report the problem returning later on.

We’re interested in finding out if any more of our readers have been affected by this problem, and if they have found any successful way in which to mend their Mac in such cases.

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