My compliments!
Coulnd't have resolved this one (the Kext Wizard did the trick for me).
Took me some time but with all the information and the IOPCIFamily.kext Mountain Lion file I found and downloaded in this conversation (took me most time to figure that one out as mine was gone from TimeMachine too, and on my other MacBook Pro 10.8.5 I couldn't find it at all), together with the Kext Wizard.app (thank you all other people here for uploading!) it worked 100% so far. This is what we're all here for. Together we fix it. Great work,
For the one's who're still struggling:
I'm one of those MacBook Pro 17-inch, Mid 2010 users. After reading most complaints I worried if mine would ever work again. For all other who didn't work it out, here's my preferences:
MacBook Pro 17-inch, Mid 2010
Mac OS X 10.9.1
Processor 2,66 GHz Intel Core i7
Expresscard LaCie SATA II ExpressCard 34 (previous blue type, not the orange one).
External Disks Attached 2 LaCie Disks.
Conclusion Both mount and work 100% with FinalCut Pro 7
Here's a message to the crazy one's at Apple:
Shame on you lazy cheats!
When users are getting more clever than developers one might think it's going the wrong direction.
It seems more of a nasty marketing trick to force people to buy new Mac's. Rather help your customers instead of having bad publicity. Does Apple have any idea how bad this is for the environment? All those disks and Macs and hardware needing to be replaced ending up on junkyards while still good to go.
I want to keep using my 17" MacBook Pro as I love it and need the larger screen size for the extra windows and tools. As it isn't being discontinued with the new MacBook Pro models (a lame idea in the first place) at least don't frustrate users with very poor service, or actually: no service on this one at all.
Steve Jobs would have fired the one's being responsible for this major stupidity.
Now fix it as soon as possible with Mac OS X 10.9.2 or do get the broken glass field treatment as discussed earlier in this conversation.
And while we're on it anyway: where is the long expected 4K Cinema Display.
Please do support your early hour users (I use and invested major bucks in Apple since 1986) and do pay some respect.
We make you keep your job.