I am using the same QCAD, just german version. Crashing happened to mee too, when I tried directly to export to pdf without prior Print preview.
When doing print preview first, it didn't crash, but produced empty files.
Are you having a format other than A4 or A3? It seems to have problems there.
on Windows XP
When I try to export my schematics (.dxf) to pdf, QCAD crashes.
I also tried to export as bitmap, but the generated files are empty.