Snap to Grid behavior not working?

I recently upgraded from CS3 to CS6. To my eyes, Illustrator's Snap to Grid functionality is either broken—or I'm not understanding a (new?) option.

Use case: I set-up a grid with 1/8" spacing. I paste a 1/2" x 1/2" object from another file, or just copy and paste an existing one in the same file. I want it to sit, say, 2" from the top, and 4" from the left edge. In CS3, I could just use the arrow keys on the keyboard to move the object around, and its edges would precisely snap, as expected, to the grid, with no muss or fuss. If it was an uneven size, the edges would snap, making it easy to at least align the left and top edges (for example) where I want the object to sit.

In CS6, this really just plain doesn't work—either with arrow keys, or moving the object with the mouse. The objects are always—ALWAYS—some fraction "off" in one direction or another. And yes, I know it sounds like the Snap to Grid is off, but it's not. The object moves by increments of the grid (1/8" in my example), but the object is not grid-aligned, and cannot be made to be. I can arrow-key the object all over the workspace and it won't snap properly. The only way I can find to accurately position the object is open the Transform dialog, and enter the measurements by hand.

Quite honestly, that's a pain in the butt, and it's made literally everything I do in Illustrator take roughly twice as long. This is improvement?

I am hoping I "just don't get it." That there's an option mis-set somewhere in here. Maybe it's related to moving from Windows on CS3 to Mac on CS6, who knows. What I do know is I'm starting to hate Illustrator every time I have to fire it up these days.

Anyone else see this? Anyone have any idea how to fix it? File a bug report?

ADDED:  In playing with this just after my original posting, it appears that the described issues occur only with groups of objects. For example, a 1/2" x 1/2" icon composed of a square for its outer dimensions, with some other stuff layed on top, then grouped, and moved as a whole. (Although whether it's grouped doesn't actually seem to matter—an ungrouped, multi-select of the same sort behaves the same way.)