I just started happening this week but I'm not able to drag and drop pictures from the builder on the left side of the campaign creator to the actual email layout. I'm on a PC and tried it in Chrome and Firefox and the same thing is occurring in both browsers.
Thank you for reaching out to the Community about your emails! Working in different browsers like this is a great troubleshooting step to take. We would however also recommend testing your account in a private/incognito window. Doing so helps to see if there are any 3rd party add-ons that could affect how Constant Contact works. We also would like to collect a few more clarifying details on what exactly you are experiencing. Are you unable to see the pink indicator line when moving blocks into your campaign? If you do see it, is it freezing or even moving to a different section than your mouse is on? As a workaround users have double-clicked on a block to automatically add it to the bottom of an email. Once it's placed there it can then be dragged to its intended section using the click and drag icon on the right-hand side.