I have had this happen with a FW800 drive before as well. It acted as if premission was set to read only, even though that was not the case. Honestly, I wish I could remember what I did to fix it. I believe I just changed drives, which doesn't help you all that much unfortunately. However, it may indicate that a SSD drive is not necessarily the problem.
-btw, how does PPro look on your retina? I heard until they update the software, it may look a little fuzzy. (I picked up a MB pro the other day, but went for the standard due to the backorder.)
I have not been able to access PPro yet since I did not want media written to my system drive (er... flash memory) and it would not write to my external SSD. And I'm out of the country with no other computer or drive with me.
Other non-retina apps look decent enough and I can't tell a difference. What's impressive is the size and speed of the machine.
After digging through a number of other forums, found the solution. I needed to clear Premiere's caches. It would then recognize my external drive and write to it. Definitely something Adobe needs to address.