In LR development module, I suddenly get very blurry images, no matter what extension (see screenshot attached). In library module the pictures are still okay. Has anyone encountered this problem before?
The image data may be corrupt. It could be a bad card, a bad drive, a bad cable, a bad reader or some other hardware issue. The recommendation is to start eliminating hardware components in the hopes you can find the defective (or not connected correctly) component.
File browsers may show you a correct embedded JPEG where as Lightroom shows you a (corrupt?) rendering of the raw file data.
Also check your Graphics card drivers are up to date-
p.s. i don't think the adobe website, and forums in particular, are easy to navigate, so don't spend a lot of time searching that forum list. do your best and we'll move the post (like this one has already been moved) if it helps you get responses.