Instagram pictures have been wonky inside of Twitter ever since Instagram disabled Twitter cards in hopes of driving users to its own web interface. Now Instagram pictures aren't showing at all in Twitter's native web client, and that change is permanent.
From now on, links to Instagram pictures on Twitter will work as links and nothing but. If you want to get back instant-show functionality for your filtered pictures, you'll just have to switch over to the Twitter version that's due to launch sometime before the holidays. A Twitter status blog update confirms this is due to Instagram turning card support all the way off; this is no glitch. It's the end of an era.