2D lines suddenly changed to 3D

Hi all,

I have a big regional dataset with a large number of 2D seismic lines and a single 3D cube. I was moving a timeslice through the 3D cube, when Petrel crashed. As I re-opened the project and tried to display a 2d line it would not display. After looking into it I noticed all 2D line symbols had changed into 3D seismic symbols. I have consulted the help, but there seems no information to be found about changing those lines back to 2D lines. Even in the Survey manager they are all listed as being a 3D "type". I reloaded one line and it was automatically assigned a 2D status and displayed correctly. Is there a way to change 3D datasets back to 2D?

I really don't feel like reloading all 2D seismic lines, furthermore my interpretations will then be lost. Backups do exist, but date pretty far back. Hope help can be found here!

regards,

Willem