Flex compiler produces inscrutable "identifier.character" error

I inadvertantly inserted a "\" at the top of spark/defaults.css during a flurry of unrelated edits. Subsequent compilations failed with a "identifier.character" error. No other information was provided. Needless to say, this proved to be rather confusing.

Corey tells me that the problem is in StyleParserErrorTranslator.java, which lacks a case statement for this error.