[sdiy] EAGLE beginner question

[ChristianH]

Hia ll,

I finally started doing projects with EAGLE (5.0 that is).

Occasionally, I get yellow "unrouted" lines on a board, ending at no pin.
If I rip up such a yellow line to get rid of it, the attached traces are
ripped up as well, which is definitely not what I want.
Sometimes there's a yellow X at the line's end (which I suspect is a
zero length unrouted line). 

Is this some expected and explainable behaviour, or is this just a
software glitch?

Christian