I'm getting a similar, bizarre behavior in section/elevation windows. In my detail .PLN's, formerly of and working fine in AC9, MOST (but not all) windows zoom to near the Andromeda galaxy when I Fit In Window.
I deleted piece by piece the details, but nothing seemed responsible. I deleted everything and typed in a letter A, and it still did it! I tried dragging my all-selected detail (a small modular box with the detail in it) to the Origin in the S/E window, and it zoomed in a bit more! I dragged the detail to the opposite side of the window, and it zoomed in close to right! One more drag and it zoomed in all the way.
So what's THAT craziness all about? I'm hoping not to have to go through a couple hundred details with this arduous method of correcting. And I NEED the details to be in the center of the window, because we publish each detail .PLN to a single PDF, then print out four pages of the PDF per sheet to create an updated binder of all current details.