Double clicking the breakline tool will produce a break at an edit handle. If you go through the edit object parts tool, which i pin to a tool bar using the tool menu>customize toolbars (which give you a list of tools you can then drag and drop on your tool bar) when doing a lot of CAD, it will "explode" anything you select. This can be bothersome if you arent on top of it, and undo's are useful (cntrl z) if you disconnect things you dont want to disconnect.
also, section lines can be locked, ect ect. try selecting what you want. Use the "enter" key, which will toggle through nearby objects. If what you are trying to alter doesnt highlight, its locked, and theres nothing to do but go through your layer display and find it.
