I have recently installed MacTeX.pkg (http://tug.org/mactex/) as well as Texmaker. I have this famous "Log file not found" problem, and I'm still stuck with it even thought I have already checked many other questions that were previously asked.
Texmaker is pre-configurated to work with MacTeX: there is nothing to change to the settings (if MacTeX is installed correctly, of course). To reset the settings: "Options" -> "Settings file" -> "reset settings". And a new document must be saved with a
.tex extension (without spaces or special characters in the name) before being compiled (if the message "log file not found" is displayed, it means that the compilation has failed). As you seem to be French, take a look here: installation de MacTex2012 et Texmaker
The error may be due to a format issue. Try run
to regenerate the format.
I had the same problem with Texmaker on mactex...it was being caused by me checking the setting the 'use a "build" subdirectory for output files'. I don't know why this happens, it runs well on a windows version.