Remote writer: export to pdf not working anymore: conversion error

Remote writer: export to pdf not working anymore: conversion error

Hello,

When we try exporting files with remote writer api we get an error since the beginning of the week.
"Conversion error"

So we can not export to any format (pdf/html/ etc)

We are using firefox 17.0.1 on a Win7 os  (but also on mac it is not working)

Please can someone have look at this?

Many thanks
Nicolas