Follow below steps.
Click on Finder and hold command + shift+ G keys on your keypad.
In the go to folder window type exactly ~/Library and click on Go
Open Application Support > Adobe and right click on Lightroom folder and select get info
Under sharing and permission Click on lock and unlock it
Click on + add your current user name and administrator if not added
Then give Read and Write permission for Admin, system, everyone and (your user name)
Click on gear icon and choose apply to enclosed item
Then Click on Lock
Launch Lightroom and check.
I have set myself for read & write permissions along with all other listed users. Didn't solve the problem. Made this change a couple of days ago and sense then have reinstalled and rechecked permissions. Still a no go. The one difference between the Mac Pro and MBP installation is on the MBP, I installed Lightroom and later upgraded to Yosemite. On the Mac Pro I first upgraded to Yosemite and then tried to install Lightroom.
Here is what the system sees for Lightroom:
Adobe Photoshop Lightroom 5:
Version: Adobe Photoshop Lightroom 5.6 
Obtained from: Identified Developer
Last Modified: 11/6/14, 9:43 PM
64-Bit (Intel): Yes
Signed by: Developer ID Application: Adobe Systems, Inc., Developer ID Certification Authority, Apple Root CA
Location: /Applications/Adobe Photoshop Lightroom 5.app
You are giving permission to different Lightroom folder, there will be two Library folders on your MAC, we need to open User library and give full permission. Please follow my steps and open Go to folder. In the Go to folder window type ~/Library, not /Library. Then Open Application Support > Adobe and give full permission for Lightroom folder.
You are correct. I see the difference and changing the permissions does resolve the problem. I very much appreciate the fix.
I am glad that you were able to fix the issue
Thank you! Your fix came up on top of my google search for good reason.