Sounds more like a graphic card issue than a LR issue.
Please post the type of system you have, Desktop or Notebook, what OS you are using, Windows or OS X, and what version of the OS is installed.
I know this is an issue on Mac notebook computers as there have been many recalled for faulty graphic cards.
In Windows the F5 function key does a screen and or app refresh. Not sure if there is something similar on Mac OS X.
Try that the next time you get the streaks and if they go away then it is a hardware issue.
this is almost always a hardware malfunction in the transfer of the photos from the camera card to Lightroom.
It could be anywhere in the transfer chain, camera card, card reader or USB Cable/USB Port, hard disk, memory.
You need to try performing the transfer again using different hardware, and if possible perform the transfer on a different computer.