I am using Lightroom 6.3 after upgrading straight from 6.0.
My computer runs Windows 7.
When I try to move to the Develop module from the Library, more often than not, the screen freezes, the blue doughnutty thing spins on and on and the header of the window reads
Lightroom Catalog - Adobe Photoshop Lightroom - Develop (Not Responding)
I have to crash out of Lightroom and try again...