It appears a bug has been introduced in Git plugin 1.1.16:

If I set the branch specifier in the "Branches to Build" section, I always get the following error.

ERROR: Couldn't find any revision to build. Verify the repository and branch configuration for this job.

The only way I found to resolve this is to get rid of the branch specifier and replace it with **. However, I only want to build a specific branch in our Git repo, so in the meantime I've rolled back to 1.1.15 where this functionality is working just fine.