I get the following error message when starting Lightroom 5.5 for Windows 7 64 bit: Lightroom encountered an error when reading from its preview cache and needs to quit.
I've uninstalled and reinstalled Lightroom with same error.
Using your system browser, go to the folder containing your catalog and delete the folder with the extension .lrdata. Then start Lightroom, and it will start and create a new previews folder.
Retrieving data ...