This may have already been posted/answered before but I have no idea how to describe this so I doubt I would find anything by searching.

 

I'm using AutoCAD LT 2009

 

Say you have two lines on the screen and you want to move both of them at the same time. Instead of dragging a box over the two lines you individually pick them by clicking on each of them separately. When you click on one of them it highlights it however, when you click on the other line it highlights the new selection but un-highlights the first one. I have since discovered that if after clicking on the first line I hold the shift key I can click the second line and both are still highlighted. I have no idea whatsoever as to what I have done and I would greatly appreciate some help. It's driving me mad!