Sounds like a bad wheel build to me. Spoke prep is always a good idea. I have used blue Loc-Tite on wheels I ride a set I did for myself and have had zero problems. A local tri athlete uses a set I built for him using the same method and loves them. Also Sapim makes spke nipples that are self locking. I built a set using those for my wife and they are superb. As a matter of fact Sapim spokes is what I use exclusively. I figure if Lance and the USPS team uses Sapim they are good enough for anyone else right?