May i know are you using windows or mac.
I am using Windows 10.
I just tested: I can start LR 5.7 without problems.
Try the following: With Windows Explorer, navigate to C:\Users\[your username]\AppData\Roaming\Adobe\Lightroom\Preferences
Open the file Lightroom 6 Preferences.agprefs in a text editor, like Notepad.
Very close to the end of the file there is a line that says useAutoBahn = true, - change this to useAutoBahn = false,
Save and close the file. Now try to start Lightroom.
I did a reboot, changed the entry to false, saved the file and started LR but with same result.
Just to be sure, try to reboot again.
I know this can be necessary on a Mac, probably not on Windows, but it is worth a try.
Now it works :-)
To do a reboot after changing the preferences file was the solution.
I still get an error that the server is fully load but after a retry LR is finishing starting.
Thanks a lot.
I have the same problem again. I can start LR 5.7 but not LR 6.3. The preference file is still on "useAutoBahn = false".
After starting LR 6.3 the main frame pops up and then the splash screen. And then nothing more happens.
Shuting down is not possible even with task manager. Only rebootworks.
I tried several reboots this evening but LR 6.3 never started.
When you upgrade to Windows 10, your monitor profile will be replaced with an OEM (manufacturer's) profile. These profiles are notorioulsly bad, and can, among other things, cause Library and Develop to display different colors. Lightroom is particularly picky about the monitor profile, and will let you know if it's not happy with it. A profile that Photoshop finds perfectly allright can cause problems with Lightroom.
It is possible that my memory fails me here, but I think I have seen one account of a bad monitor profile causing Lightroom to freeze at the splash screen.
If this should be the problem, it can be fixed temporarily by setting the monitor profile to sRGB. (you should in any case calibrate your monitor with a hardware calibrator to create a custom monitor profile)
In the Control Panel, choose Color management, and add the sRGB profile, then set it as Default profile. See screenshot (from Windows 7) below. Now try to start LR.
If this doesn't work, try uninstalling and reinstalling LR. You will of course have to edt the preferences file again before trying to start LR.
Setting a sRGB profile as default was not the solution. The failure keeps the same.
Now I tried to deinstall and / or overinstall LR6.11. I tried several times yesterday for some hours without success, setup hangs up.
Today deinstalling was successfull and also installation of LR6.11 started with the second try.
Now installation tells me that my serial number is blocked. And support is available from 9 am to 5 pm during my work time when I am not at home. No contact via email possible. This is really frustrating :-(
Just chatted with the support:
After deleting ..User\AppData\Roaming\Adobe\Lightroom\Preferences\Lightroom 6 Preferences.agprefs Lightroom deactivats all plugins and then started successfully.
So one of my plugins was the problem.