The godfather of technical analysis, known as Dow Theory, says transportation and industrial stocks must advance together for market gains to last. The most bullish signal possible is when the two groups hit record highs simultaneously.

That happened in October, and the subsequent uptrend has yielded 17% in returns for the Dow Jones industrial average.

So it's smooth sailing for stocks, right? Not quite. The situation is not that simple for stock bears.

Recent strength in the Dow propelled the index to a record high on Monday, but the associated transportation index did not reach one, and that lack of confirmation has troubled some market pessimists.