After updating, Lightroom was working for a while, but now when I try to open it, I'm getting an error message "Unexpected error opening catalog". Trying again does not work and whilst I can find catalog folders under Lightroom backup, they appear to be empty. There are backup files from my previous Lightroom 5.7. Incidentally, if I try to open 5.7 I get the same error message. Any help will be much appreciated.
Following up, I was able to access Lightroom by right clicking on the desktop icon and then selecting run as administrator; this brought up a catalog integrity check after which the program opened. I have no idea as to why this situation arose, I've never had that problem before and did not see it listed anywhere in the trouble shooting guide. Hope my experience helps someone!.
I found the same thing by trial and error you can fix the problem once and for all by following the instructions below:
Okay, I have tested this on another machine and it should work.
Right click your LR shortcut and click 'Troubleshoot Compatibility'
Click ' Troubleshoot Program'
Click 'Program worked with earlier versions of windows but won't run now'
Click 'Program requires additional permissions'
Click your previous windows version.
Click 'Test Program' If User Account Control is on you may need to click the shield icon on the task bar and give permission for changes and then click 'test program' again.
LR should open. Close LR
Click 'Save settings for this program'