Does anybody have any pointers to what SWD files are in Flash 9, why Flash Player wants to download them sometimes, how to make ones, how to make use of them? Didn't manage to dig anything useful myself yet.
Update
I know roughly what are swd files used in Flash8, and there is even a way to make them, but Flash 9 doesn't seem to need it at first glance, but still attempts to use sometimes.
SWD files are similar to SWF files, except that they contain debugging-specific information that the debugger and Flash Debug Player watch for.
From: About SWD files
The citation above is from the Flex documentation but applies to 'normal' Flash too.
SWD files are needed to debug content with Adobe's debugging tools. You can see this in action by publishing from Flash authoring with shift-control-enter.
The SWD itself is only needed for the debugging tool to see inside the SWF. You can throw it away once you're done debugging, and you never need to upload it to the server unless you're planning to do remote debugging.