AutoCAD MEP

[#1]

I have a drawing that i have been working on for some time now. all of a sudden when i pick add a pipe from the palette it is telling me to choose a part.

Why does this change happen and how do i fix it? 

A long the same lines i notice when i open an older 2006 adt file with pipes drawing, 2012 does not reguster the pipes as a routing style. 

Why does this change happen and how do i fix it? 

thanks

[#2]

Ive run into the problem too.

Ive noticed that if I sometimes draw a bunch of different pipe runs off to the side of the drawing, changing the routing preferences and sizes a bunch of times, and then going back to the routing preference that was giving me troubles, that the program smartens up and works again.

Unfortunately there have been times when that didn't work, and my only solution was to go back to an older version of the drawing that worked properly and copy my new work into it and go from there. 

So I would also like to know what's going on when at one second I can add to pipe runs no problem, and then the next second I can't and then constantly asked to choose a part ?

It's not because my pipes are skewed, or the part doesn't existing, or anything, because it works fine again once I've used one of the above solutions..