To reset your user origin back to the project origin, simply double click on your user origin button, which is by default in the bottom left of your coordinate box.
This shouldn't matter when it comes to creating a linetype though, as the center of the line is determined by the origin location when the line elements are copied to the clipboard. If you want your insulation to appear on the 'upper' side of the vector you chose to create it with, then simply move all of you line elements so that they sit on and above (in the y direction) of your origin. See the attached image.
The hardest part in creating a linetype is getting it to scale correctly. Here's a little help guide - hope you can get your head around it!:
http://www.graphisoft.com/support/archicad/archiguide/linetypes.html
Cheers,
Link.