Apple is always trying to push people ahead
They would love you to have their latest Yosemite system that still has enough bugs i read... even with WIFI...
Also they gently remove older software so you have to have the latest system...
Do you have iPhoto? for that is required to be able to install these raw compatibility updates...
if you have updated iPhoto to the latest possible version on your system then try the raw compatiblitiy updates as mentioned. ( software update will get them for you)
If you have to upgrade to 10.8 - if still possible... that is no big deal- just download it from the Appstore and install it with all the software updates
If Apple does not 'sell' 10.8 anymore try Mavericks ( 10.9.5)- it is still their most stable system at the moment.
If they do not 'sell' that either you are forced to try 10.10.2 yosemite i guess
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I think Lightroom will be able to open the files anyway.... Also try installing Sony camera software... the problem is usually the thumbnails, not the rendering of the complete image...
Install the 30 days free Lightroom version to see if that helps...
cheers.. pk
PS
if you upgrade your system do not forget to make a (timemachine) backup first...