A new version of the lettre class has been loaded on CTAN (ref. number 3.000
instead of 2.353).
The major improvement from the point of view of LyX is the addition of class
options a4paper, letterpaper, legalpaper, executivepaper,
b5paper, et a5paper (a4paper was hardcoded before, leading to incorrect pages
sizes when US letter formats were used). Now one can select US letter in the
Document>Settings>Page format to get the correct result.
The mechanism allowing to print the address and other informations of the
institute has changed: now the file containing the information is named
The backward compatibility is guaranteed (old file ames are recognized), and
this feature being not supported in the LyX template, I think that nothing has
to be done from the POV of backward compatibiliy in LyX. I will just point this
out in the note at the beginning of the template. Is that OK?