The subject line pretty much says it all: some marginal notes (beginning of the second page) do not appear on the correct side. (The question is: how can I fix this automatically?) Below is a MWE that I got from my code, where I removed as much text as possible (and replace the missing text by a vertical space). I tried to remove some equations and the itemize environment to simplify things further, but could not get the right value of \vspace to still illustrate the problem.
This is a partial answer to my problem ... If I write \strictpagecheck before each \marginpar and if I explictly write \marginparmargin{outer} (which is supposed to be the default), the notes on the second page all get positioned on the correct side. The problem is that the notes that were previously on the wrong side now partly overlap the other ones.
Commenting on an answer which was deleted by its author: I do not want the oneside option as this is going to be printed as a book. Also, I tried sidepar and it definitely does not work: the notes on the first page are on the wrong side and some of the ones on the second overlap. Eventually, I will want to add figures as well as text in the margins.
\documentclass[11pt,openany]{memoir}
\setstocksize{11in}{8.5in}
\settrimmedsize{\stockheight}{\stockwidth}{*}
\settypeblocksize{9.0in}{30pc}{*}
\setlrmargins{0.7in}{*}{*}
\setulmargins{1.0in}{*}{*}
\setheadfoot{30pt}{26pt}
\setheaderspaces{*}{30pt}{*}
\setmarginnotes{0.2in}{1.5in}{0.2in}
\checkandfixthelayout
%
\begin{document}
Some text to get things started.
\vspace*{17cm} % to minimize the amount of text on the page.
Some text\marginpar{First note} with some notes in the margin.
Some text\marginpar{Second note} with some notes in the margin.
Some text\marginpar{Third note} with some notes in the margin.
\begin{itemize}
\item First item.
$$A=B$$
\item Second item.
$$A=B$$
\end{itemize}
Yet more text with a note\marginpar{Fourth note} followed by an equation.
$$
A = B
$$
Now we can see the problem.\marginpar{This note is on the wrong side.}.
With some more text\marginpar{And another note on the wrong side.}
so we can perhaps start seeing what is going on.
Some text added with other notes and a reasonably long sentence to keep
the notes somewhat separate\marginpar{Note 1 on the correct side}.
Some text added with other notes and a reasonably long sentence to keep
the notes somewhat separate\marginpar{Note 2 also}.
\end{document}
\strictpagecheckin the preamble and it works fine for me. Remember that you will need several runs (the feature use labels to verify pages) – daleif Mar 29 '12 at 20:47\marginparare in the first line after a display that ends a page. You can manually fix it by issuing\clearpageafter the display and adding\noindentif you don't want an indent. With\strictpagecheckthe second marginpar overwrites the third and fourth. :( – egreg Apr 11 '12 at 14:12\usepackage{marginfix}to the preamble, the problems with overlapping and wrong margins disappear, but now the fifth and sixth note are on the first page :-( Which leads me to the crude theory that somehow the first line after the displayed equation was considered for the first page but split off later, when the marginpars were already placed. There is some strange code for handling marginpars in\@specialoutput, followed by extremely involved code in\@doclearpage. If the line is split to the second page at this point, the marginpars are already placed. – Stephan Lehmke Apr 11 '12 at 15:29