Using draftSightV1R1.4 on fedora16

An hour ago during working draft sight crashed down and saved 2 hours work in an empty file 0kb, the bak file is about 720kb. I have still a recovery file from the morning, but there is still some work gone which i want to have back.

As i try opening the dwg it is emtpy; following some recherches in the internet restoring the dwg file is just renaming the bak to dwg.

After renaming i opened the file with draftsight, that displayed the message "Zeichnungsdatei muss wiederhergestellt werden Möchten Sie fortfahren" (installed in german, my short translation "File needs recovery" Yes/No)  where i said  Yes.

Than draftSight opens the 720kb file without any line on the screen, even when i zoome out! 

Does anybody knows likewise behavior?

Does anybody know a good recovery procedure on dwg, baks?

Best regards