Unknown error when compiling project

I have completed a Connect IQ watchface for FR230, 235 and 630. Now when I compile the project, it keeps returning an unknown error code 1 and compilation has failed. Anyone familiar with this? What are common export errors?

I also get this error when exporting a sample project.

This has been seen by many people, including folks at Garmin, but they still haven't found the cause. For me, I find if I just do it a few times without changing anything, it will work. Some people copy the command line for monkey C from the eclipse console window and do it from a command prompt, and that works too.