Could you please let me know the exact version of Lightroom installed on your computer?
Also which operating system are you working on, windows or mac?
Im on the OS X el captain 10.11.16 mac and have the LR 5 5.7.1 edition
Does it happen with all the images in catalog or some specific one's?
Also did you try with a newer catalog and see if the application still locks or not?
I haven't tried a new catalogue, but up until two weeks ago it was working fine. It happens as soon as LR opens on the main screen. The program works fine for editing, but like I said, it just locks, can't be moved, can't resize window etc etc.
Before trying a test catalog, optimize the current catalog and then check with the same catalog.
Optimize the Lightroom catalog by choosing File > Optimize Catalog.
I optimized the catalog and it didnt work and then I tried a test catalogue and still nothing. I think I may have solved the problem though while I was tinkering around. I went down to the screen views at the bottom left and went to normal screen view. Then I was able to change and maneuverer the window like I did before. I just don't know how it ever got switched to that setting in the first place.
Thank you for sharing the solution with us.