As we have a stable firefox 3.5 in the meanwhile, and the backporters team refused to backport it to hardy (see bug #395167), I removed the distribution's firefox package and installed the vanilla build from mozilla.com (and updated it since to 3.5.2). With this package, not the ubuntu one, I did some test and had no crashes printing to file in pdf format. This is not exactly what you asked, but I am not willing to use an obsolete version any more.
As we have a stable firefox 3.5 in the meanwhile, and the backporters team refused to backport it to hardy (see bug #395167), I removed the distribution's firefox package and installed the vanilla build from mozilla.com (and updated it since to 3.5.2). With this package, not the ubuntu one, I did some test and had no crashes printing to file in pdf format. This is not exactly what you asked, but I am not willing to use an obsolete version any more.