Strange error converting ePub to PDF

Indeed, the ePub has some links, but no resource needs to be downloaded or anything else treated, just links to the outside (webpages).

What to be done to get rid of this error? I use 4.2 but on the other computer with an older version (2.5 I think) I never ever had any issues converting to PDF, even linked photos from the outside world, apart from some minor issues.

Thanks in advance
Ghitulescu