I have a Flash project, and it has many source files. I have a fairly heavily-used class, call it Jenine. I recently (and, perhaps, callously) relocated Jenine from one namespace to another. I thought we were ready - I thought it was time. The new Jenine was better in every way - she had lost some code bloat, she had decoupled herself from a few vestigial class relationships, and she had finally come home to the namespace that she had always secretly known in her heart was the one she truly belonged to. She was among her own kind.
Unfortunately, Flash would have none of that. Perhaps it had formed an attachment. Perhaps it didn't want Jenine to be decoupled. Either way, it clung to the old, perfect version of Jenine in its memory. It refused to move on. It ignored her (function) calls. It tried to forget her new, public interfaces. Instead, every instance of Jenine that it constructed was always a copy of the old version, down to its classpath:
We fought. I'm not proud of some of the things I said or did. In the end, in a towering fit of rage, I deleted all references of Jenine completely. She was utterly, completely erased from the system. My cursor fell upon the "Empty Trash" menu option like the cold lid of a casket.
I don't think Flash ever recovered. To this day it still clings to the memory of Jenine. Her old, imperfect definitions still float through my project like abandoned ghosts. Whenever I force Flash to compile, it still lovingly inserts her into my movie, nestling her definition in amongst the other, living classes, like a small shrine. I wonder if they can see her.
Flash and I don't really talk anymore. I write my code, it compiles it. There's a new girl in town named Summer who looks almost identical to Jenine, as if someone had just copied her source-code wholesale into a new class, but Flash hasn't shown any interest. Most days it just mopes around and writes bad poetry in my comments when it thinks I'm not looking.
I hope no one else has had a similar experience, that this is just a singular, painful ripple in the horrifying dark lagoon that is the Flash code-base. If, by some fluke chance you have, or you have any idea how to erase whatever damn cache the compiler is using, please, please help.
Flash still has the ASO file, which is the compiled byte code for your classes. On Windows, you can see the ASO files here:
C:\Documents and Settings\username\Local Settings\Application Data\Adobe\Flash CS4\en\Configuration\Classes\aso
On a Mac, the directory structure is similar in /Users/username/Library/Application Support/
You can remove those files by hand, or in Flash you can select Control->Delete ASO files to remove them.
Do you have several swf-files? If your class is imported in one of the swf's, other swf's will also use the same version of the class. One old import with * in one swf will do it. Recompile everything and see if it works.
Try deleting your ASO files.
ASO files are cached compiled versions of your class files. Although the IDE is a lot better at letting go of old caches when changes are made, sometimes you have to manually delete them. To delete ASO files: Control>Delete ASO Files.
This is also the cause of the "I-am-not-seeing-my-changes-so-let-me-add-a-trace-now-everything-works" bug that was introduced in CS3.
I have found one related behaviour that may help (sounds like your specific problem runs deeper though):
Flash checks whether a source file needs recompiling by looking at timestamps. If its compiled version is older than the source file, it will recompile. But it doesn't check whether the compiled version was generated from the same source file or not.
Specifically, if you have your actionscript files under version control, and you Revert a change, the reverted file will usually have an older timestamp, and Flash will ignore it.