Unable to add photos to collection

[photobyderek]

After importing images into LR I am unable to drag them to a collection. I have watched the tutorial several times to ensure I am doing this correctly. Yesterday there were no issues, today I can't add any imported image to any collection. What am I missing or what is an obvious mistake I am making without realising it? 

[photobyderek · Accepted solution]

I would like to be able to easily delete this post. I have since found the solution:

Drag using the image itself, not using the grey border. 

[Rikk Flohr: Photography]

We don't like to delete posts as others may come along who have the same question and can benefit from the solution.