If you have a frame selected and then hit Command-D (place), sometimes the incoming image gets placed in the selected frame (as it should), and sometimes the cursor becomes a loaded cursor and the image is not placed.
Also, if you have a loaded cursor and then cancel the Place by hitting escape or selecting another tool, the next time you try to place an image, the previous image will also be loaded along with the new one. Are these bugs in CS6?
When choosing File>Place ensure that "Relpace selected items" is ticked.
As for the loaded cursor - I don't know what's causing that.
Yes, "replace selected items" is checked. Like I said, sometimes it happens one way, sometimes it happens the other way. Particularly when the loaded cursor starts acting wonky, that's when it stops placing content in the selected frame.