I have the latest downloadable version of LR5. It crashed while it was createing 1:1 previews during an import. After a Win7(64) restart, it shows a message that LR needs to quit because it can't read the preview files and it will try to fix it the next time is launches. I get the same message the next and every subsequent time it launches so I can't launch LR at all now.
I get that the preview file got corrupted somehow. Is there some way to fix this problem without building a new catalog?
Use Windows Explorer to open the folder containing your catalog. You will see a folder with the extension .lrdata. You need to delete that folder and then start Lightroom again. Lightroom will generate a new previews folder.