It's incredible, the project even builds. It's just I can't open those files in the EDITOR.
For god's sake there must be a fix for this
I just restarted Flash Builder TWICE MORE, and now everything works.
Not once, twice, because the first time it said "workspace in use or cannot be created, choose a different one", so I closed FB and opened it again.
I'm so sick of this sh***
Just come across this also, incredibly frustraiting, some files, not all refuse to open in the IDE some of the time.
They exist and open fine in a normal editor such as Sublime or Textmate but not in Flash Builder.
Restarting the IDE is the only way I have found to fix this, seems to happen randomly to different files.
I had the same issue with flash builder 4.6
Restarting FlashBuilder a few times solves this weird issue.