P: Pixelated or blurry preview in Library Loupe LR 4.3

Unfortunately, this didn't fix the problem for me.

I can confirm this observation. Perhaps I can add that it happens when a photo is viewed after a image that has been rotated in lightroom.

In fact, only if the rotation is +/- 90°.
Between two pictures that have been rotated the problem doesn't appear.
So it occurs when lightroom changes the rendering mode.

Update-using a solution suggested in another topic, I deleted Previews cache and restarted LR and this seems to have fixed the problem (for now).

I am noting a similar issue. I thought some of my photos were blurry. Then I zoomed 1:1, and they were fine, zoomed out: Not blurry anymore.
If I zoom in, or select "render 1:1 preview", it goes away.
Yet my standard (not 1:1) preview dimensions are larger than the screen I am viewing on, and it only happens occasionally (1 in 20?).
Changing between photos with different orientation, as mentioned by Rebecca, does seem to triggering
Note, this is all occurring on my 2nd display.

This problem also appears if I switch images while within the Print module - preview is blurry. It is impossible to accurately judge a potential print with this bug (I assume it is a bug!)This happens every time I do this; switching to a different print template is fine though.

Using a brand new iMac, Mountain Lion and 16 GB RAM.

Please fix this, Adobe!

Thanks. I've added your notes to the bug database.

Looking through the forums, it seems like the problem of blurry images being displayed in Library mode that look sharp in Develop mode or exported as a jpg has been reported a number of times before. I seem to have found a way to reliably reproduce the problem which I have not seen mentioned anywhere so I thought i would pass it along. It seems that if I view an image the Library module that is vertically oriented and then switch to viewing an image that is horizontal, the horizontal image looks blurry. If I switch to another horizontal image and then back to the blurry one, it now looks fine. This happens very consistently. The zoom level I am using is 'fit' which does seem to make a difference (the problem doesn't happen at any other zoom level). Hopefully this helps someone track this down and fix the problem.

Ever since upgrading to Lightroom 4.3, I've been having problems with standard previews in Loupe mode occasionaly being pixelated. This seems to happen randomly for some images. When I move from one image to another using the arrow keys in Loupe mode, sometimes an image's preview is pixelated. When I move past it, then back up to it, it looks fine. If I continue backing up, then go forward to it, it will look pixelated again. The preview is fine, but for some reason Lightroom shows it as a pixelated smaller preview sometimes, but only when going in a certain direction. Sometimes it's when I go forward to the image, sometimes when I go backward.

Mac OS X 10.7.4
Mac Pro 8x 2.8GHz (Early 2008 model)
ATI Radeon HD 5770 video card
Apple 30" Cinema Display
Lightroom 4.3

I have raised a similar (though not identical) problem in topic: "Lightroom: Monitor 2 stops updating in Develop LR4.3 W7-64. " I don't know if they are related, though I am pretty sure I have seen exactly this too, where a low resolution display is replaced by a medium resolution one, but it never makes it to a high resolution version. It doesn't happen to me every time though.

Same problem here with 4.3 using OS X 10.7.5. The problem did not occur with 4.2.