Lenghten, Dynamic command causes random crashes

I use the "lengthen" command with the "dynamic" option quite often. This command is neat because it lets you manually drag a line to any length (similar to extend). I made a toolbar button for the command that works fine...most of the time. Every once in a while when I pick the button for this command DraftSight prompts an error message & quits, but fortunately my drawing(s) will be saved OK, being renamed with "recover" in the file name. Why does dynamic lengthen cause this & only once in a while? It'll happen whether I have only one drawing open or if I have multiple drawings open. My PC has plenty of RAM (4 GB) & an excellent graphics card. Does anybody else have this problem?

Help?

Thanks