Here is my problematic code:
\begin{tikzpicture}
\draw (0,0) to [bend left=20] (3,3) node[midway] {midway label};
\end{tikzpicture}
I wanted to put a label midway of the line, but instead the label is at (0,0).
If I remove [bend left=20], the line is not bended, and the label still misplace.
If I also remove to and replace it by --, then it's works fine, but my line is not bended any more.
\begin{tikzpicture}
\draw (0,0) -- (3,3) node[midway] {midway label};
\end{tikzpicture}
Works fine.
The problem occurs with MacTeX 2011 and MacTeX 2012.


[bend left=20]in your post) can be formatted by enclosing them in backticks. – Jake Jul 22 '12 at 9:29