hello, very often i got message from Lr4 that my catlog is scorrupted and caby book where he says. this kinf od n't be repaired. I restore catalog from the last backup I save every time I quit Lr.. I read SKelby book, where he says this kind of disaster happend to him only once. 
pls can u help me ehy does it happen to me very oftne and I think i use lr4 catalog in wrong way..
thank you in advance, Irma