something not good

 From:  BurrMan
3011.7 In reply to 3011.6 
With the first model, You would use the "Merge" command to have your curve "not seperate" in that area.

Select surface and run trim and select curve. Remove inner surface. Select both edges of new trimmed surface and type Merge<enter>. Ths will combine those 2 edges back.

Michael will probably explain what is going on there.