This is the most obnoxious error and it wastes incredible amounts of time every day.
After getting a compile error in a Flash Professional / Flash Builer Project, the thing will refuse to update the swf with any new changes to the code. Cleaning the project is irrelevent. Even added trace statements don't show up. Sometimes restarting Builder will help, sometimes it wont, but since this happens every few errors or so, it is impossible to manage this way.
The thing just continues to launch an old version of the swf no matter how much you've changed the code.
Also if you try to report bugs in Adobe for Flash Builder it tells you to click a special "Flex /Builder bug report form" which is a dead link to nowhere.
Most likely it seems that Flash Builder or Flash Professional thinks that the swf is still open and in use (even though it absolutely is not) and so refuses to overwrite it.
Rather than tell you this it launches the old version of the swf and pretends a compile has gone through.
Also there is absolutely no way of telling it that the swf is NOT in use.