# Error Message: "Lightroom encountered an error when reading from its preview cache...



## Betserella (Sep 9, 2012)

I recently installed Lightroom 4.0, and upon opening it, began installing 4.1.  My computer froze halfway through that and I had to restart.  

Now whenever I try to open Lightroom, I get the following error message: "Lightroom encountered an error when reading from its preview cache and needs to quit.  Lightroom will attempt to fix this problem the next time it launches."

I have tried using the installation DVD to repair the install, and also to remove it and reinstall it.  Everything I try results in this same error message.  

Any ideas how to troubleshoot this?  
Thanks!  Betsy


----------



## Victoria Bampton (Sep 10, 2012)

Hi Betsy, welcome to the forum!

Don't panic, it's just the preview cache.  Find your catalog on the hard drive - usually in the Pictures folder called Lightroom 4 Catalog.lrcat by default.  You'll see a *Previews.lrdata folder there.  Rename it and restart LR.  

LR will have to rebuild previews, but then everything should be ok.  You can let LR rebuild the previews as you need them, or you can select them in Grid view and go to Library menu > Previews > Render Standard Sized previews.

Once you're happy that everything's rebuilt, you can delete the one you previously renamed.


----------



## Betserella (Sep 11, 2012)

Thank you, Victoria!  This indeed fixed the issue and I'm editing away now   Love the software so far!


----------



## IanShewan (Apr 23, 2013)

*Issues arose sharing LR using external drive with macOS and Windows*



Victoria Bampton said:


> Hi Betsy, welcome to the forum!
> 
> Don't panic, it's just the preview cache.  Find your catalog on the hard drive - usually in the Pictures folder called Lightroom 4 Catalog.lrcat by default.  You'll see a *Previews.lrdata folder there.  Rename it and restart LR.
> 
> ...



My issue stemmed from connecting my external hard drive to a macbook air while out, and working on a catalogue that had previously only ever been worked on from a windows (vista) PC.   got the preview cache error and followed the instructions above
I found two things:
LR rebuilt my previews folder but from only one of the three image folders in the catalogue.  I think it was the folder with the last opened image.
When looking at the images in the Develop Module, the only action in History is an import - the date I just rebuilt the preview cache.
All of the Develop actions performed are lost.
The preview cache is now 10mb instead of around 600mb  
The other two image folders are greyed out on a 'different' drive.  I think using the mac has changed the folder paths from a drive letter to a folder convention (mentioned in other threads) and now the PC croaked at not seeing a path starting with a drive letter?!

I don't see a way of getting back all the mods I've done on my images - any ideas?


----------



## Victoria Bampton (Apr 23, 2013)

Hi Ian

That sounds like you didn't transfer the catalog correctly - perhaps used Synchronize Folder to relink the missing files, which essentially removed all the existing files and imported them again.  When you open the catalog on the MacBook Air, you need to right-click on the folders and choose Find Missing Folder to link them back to their correct location.

Got a backup we can help you restore?


----------



## tenisaddict (Jun 8, 2013)

*success also!*



Betserella said:


> Thank you, Victoria!  This indeed fixed the issue and I'm editing away now   Love the software so far!



Had the same issue.  Repair install didn't resolve.  Renamed the file indicated, and now works properly.:nod:


----------

