The Merge Agent failed because the schema of the article at the Publisher does not match the schema of the article at the Subscriber.
I have run into this in the past.  In my experience typically this will resolve it's self by just restaring the sync process.  From the client in a pull situation, or restart from the publisher in a push situation.  

In short the application of DDL changes ran into a conflict but restarting the sync will usually resolve the issue.  And no, it doesn't start from the beginning, it should just pick up from the point of failure.

It also wouldn't hurt to make sure that your snapshot is up to date and current.