Clear improperly cached compile errors in FlexBuilder

If FlexBuilder is giving you a compile error that shouldn't be happening, and nothing you do seems to make it go away, it's possible FB is failing to clear its cache. Try going to:

workspace\.metadata\.plugins\org.eclipse.core.resources\.projects\<project>\

and deleting the .markers file. Restart FB and do a clean build.

Explanation after the break.