AutoCAD 2010 :: Can't Use CTRL Or SHIFT To Select Multiple Things (not Really DWG Related)

So this really doesn't have much to do with objects in a drawing. Say for instance, I go into the PURGE dialogue box, and I want to select multiple layers to purge, but not all of them. If I click a layer, and the hold CTRL and click other layers, the only one that stays highlighted is the one I just clicked...so using CTRL doesn't allow me to highlight multiple entities at the same time.

It's gets a little more weird using SHIFT. The conventional SHIFT method (works in Windows Explorer and other applications) is clicking an object, holding SHIFT, and then clicking another object further down the list...this will highlight both of those entities clicked, plus every single entitiy in between them. In AutoCAD (use the PURGE dialogue box again for reference), if I click an object, hold SHIFT and click an object down the list, it will highlight the last object clicked and everything in between the two, but it will deselect the original object. Also, if I use SHIFT to select multiple objects, and then go back to the original that was deselected and hold CTRL to select it, the last object that was selected using SHIFT gets deselected.