One of my LR catalogues reports of a preview cache problem and promises trying to fix it. Which does not work, instead the errror message pops us again and again...each time I do re-open LR. (Win7 64bit)
There was a similar thread on this problem for LR4 some time ago, however without a solution for the problem (http://www.luminous-landscape.com/forum/index.php?topic=66064.0
The only workaround coming to my mind is to delete the entire data in the previews catalog "nameofcatalog_catalog Previews.lrdata" directory and let LR built all the previews up again.
Any ideas, thoughts or even experience how to deal with that more elegantly, without letting LR building up all the previews again (which is pretty time consuming with D800E files and large GB panorama images).