Could you please confirm the version of Lightroom and also the operating system that you are working on ?
Try toggling the secondary display. It's in the window menu. It appears you have a rogue, partial secondary display window.
It's Lightroom CC 2015, Windows 7 64bit.
If you are using LR CC, you should also see if turning off graphics card acceleration in preferences->performance makes a difference.
Please go the Edit option from the Library Module, then go to the Preferences.
Please go to the Performance Tab and uncheck the option for " Use Graphics Processor"
Please let us know if it helps.
Ah, thanks Jao vdL, that sorted it out.