When I try saving a plain SVG file into DXF format, Inkscape locks up on me. This happens with .45.1 on my Mac PowerPC G4 1.33 GHz w/ 1GB RAM 10.4.11 w/ 11 GB free and with the 27 October autopackage version on Xubuntu Linux 7.10 with Celeron D 2.93 GHz with 512 MB RAM. No other problems.