I have been receiving this error occasionally. I use SVN for backup and versioning, and Flash Builder does not work well with it at all.
How I come across this error
I think FB may be using SVN; if I delete the ‘bin-debug’ directory, it is immediately recreated along with the ‘.svn’ directory. There are SVN conflicts and errors that cannot be ‘resolved’ or ‘cleaned’ using SVN because of this.
The solution I have found that works is to make my copy of SVN to ignore the ‘bin-debug’ directory. However, if I forget to do that, then I have had to delete either the entire ‘bin-debug’ directory or some files within it.
This creates the problem in FlashBuilder. If you delete the HTML file associated with the project, it’s doom and frustration from that point on. I have not found a good working solution – FB ‘clean’ does not work, closing the project and deleting the ‘bin-debug’ dir does not work, nor any solution I have found.
What might correct the problem
(which links to: Flash workflow and the danger of careless SWCs)
Note that I am NOT referencing the initial and recommended responses. They don’t work. I am referencing the post that talks about SWCs . . . it’s the only solution I haven’t tried yet.