Deleting lines in a sketch

[ARP58]

Just moved up to NX7.5, and I'm coming across several models (created in earlier versions) in which I cannot delete lines that are in a sketch unless you first delete any solids created from the sketch.
I have tried creating a new sketch in the same model, sweeping a body from it, and I can then delete elements out of the sketch with no problem.
Why are the old sketches mis-behaving?

 

[JohnRBaker]

Can you provide an example part?

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA

http://www.siemens.com/plm

UG/NX Museum:

http://www.plmworld.org/p/cm/ld/fid=209

To an Engineer, the glass is twice as big as it needs to be.

 

[mmauldin]

It may not be the sketcher that is misbehaving. Some older features (extrudes, rotates, etc.) require that profile curves are removed from that feature before they can be deleted or made reference. I forget when the change was made, but I still occasionally run into this situation.

 

[jerry1423]

Sometimes what I do in the sketch is convert the curve(s) that I want to be removed "reference" and then put the new curves in around it.
Then I remove those reference lines in the sketch after the feature regenerates, if I need to.