Editor V1.48
Click on File (top left of the editor), New, then DAT Level Pack... You then get an Access Violation error:
Access violation at address 0040370A in module 'NeoLemmixEditor.exe'. Read of address 00000000.
As NeoLemmix no longer relies on DAT Level packs, this menu option should be removed.
Will do.
EDIT: Removed for next update.