LR 5.6 freezes (window bar says "not responding"), not consistently, on selecting "done" while in crop tool. This is NOT a performance lag issue: I'm using a new Dell workstation with striped RAID drives, quad core Xeon processor, high end video card, etc. (Windows 7, 64 bit) Seems most often to happen during long editing session, while working my way through a large batch of new RAW files. I always shoot RAW, and have no problems with huge multi-layer files in Photoshop CC. Is it related to using dual displays? I like to have grid on secondary display while I work on developing on the primary. The crop seems to update on grid thumbnail, but primary display stops, sometimes starts to jump like a video card failure. Fixes?