This is known to happen quite often from what I have seen around the forums and other LD sources. My best advice would be to just keep thinking about lucid dreaming and make sure the motivation to do it stays. I'd also recommend taking a look at this, because it is the technique I used to get about seven lucids in a row, until I got bored: http://www.dreamviews.com/f49/all-da...gyoshi-113253/

Good luck, and hope you get many more LD's soon!