There's something that I have always considered as a design/programming problem and that I'd like to comment now.
When Lightroom didn't terminate correctly or because there was a power shortage or a system crash during the execution of LR, the catalog lock (.lock file with the same name as the catalog) might not be deleted. This can prevent LR from loading, especially when the "Load most recent catalog" option is enabled. IMHO, this shouldn't happen.
Obviously, LR tries to avoid two things when loading :
- Running two instances of lightroom.exe
- Opening the same catalog twice.
This should be controlled by two different mechanisms, instead of using only the .lock file. Preventing 2 instances of lightroom.exe from running side-by-side can be achieved by using a mutex (among other possibilities based on a system object). If the .lock file is still present when LR starts and tries to open the last used catalog, this shouldn't prevent LR from loading. LR should display a message to the user, giving him/her the choice to either load another catalog or to unlock the target catalog (that is, to delete the .lock file).
If one considers the number of posts and messages to the support saying "I can no longer launch LR" and considering that the answer is most of the time "Delete the .lock file that is stored with your catalog", I think it's now time to allow LR to boot even when this file exists. A lot of people would then avoid spending a lot of time explaining the same problem again and again.