Can't build: "bad signature: ¾2"

IDEA 12.1.2, seeing this error fairly frequently since the latest update whenever I try to build:

java: cannot access <class name>
  bad class file: /Users/cbeust/<class name>.class
    bad signature: ¾2 3  
    Please remove or make sure it appears in the correct subdirectory of the classpath.

The only way to fix it is to run `mvn clean package` in the shell and build again with IDEA.