Hi,

when activating instant preview in Tools>Preferences>Display, one can
preview a latex snippet in the lyx work area by inserting it in a
preview inset (Insert>Preview).

However, since version 3.1.0 it does not work anymore, in the sense
that the preview is not generated. As this feature is working correctly
on all other platforms, investigating a bit evidenced that downgrading
the dll to version 3.0.7 solves the issue.

I am attaching an example document demonstrating the issue. The latex
source used for instant preview is generated in the lyx temporary
directory (/tmp/lyx_tmpdir.XXXXXXXXXXXX/) but latex is never run on it
to generate the images. As lyx launches latex in a forked process, this
has to be a fork problem, but no error is issued. The forked process
seems to never run, simply.

-- 
Enrico