Drag & drop is not working to move an audio clip to a different audio track

Suddenly an icon is showing next to my cursor that looks like a circle with a line through the middle when I try dragging an audio clip down to a different audio track. I can't figure this out and would really appreciate some help. 

Is there some kind of limitation that could be preventing this action for long audio files that are more than 24 hours in length because this file is almost 30 hours long? I was wondering if the 30 hr length is somehow causing the problem because I opened up a different audio file that is only 10 hours long and I am able to cut a portion of the audio and move it to a different track by dragging & dropping it just like normal (meaning the below cursor icon does not appear).

Any ideas??