When you go to erase and touch the mouse pointer to a Line does the entire drawing get highlighted (RED)?
Go to the Edit tab and Edit object data button and click on a line.
What does it say at the top of the information box?
If it says Edit Group then you will need to Ungroup the drawing with the Ungroup button in the lower right corner of the information box.
Go to the Edit tab and Edit object data button and click on a line.
What does it say at the top of the information box?
If it says Edit Group then you will need to Ungroup the drawing with the Ungroup button in the lower right corner of the information box.