When I draw en Ellipse or an Isocircle, I can't TRIM it, because the ICAD don't find the intersection between the ellipse and any line that cross it. Someone can help me?. Thankyou.

There is an option in settings to create ellipses either as true ellipses or polylines. If drawn as polylines you can do more with them, but if already drawn as true ellipses you can't make them change.