I have noticed quite a few people coming acrosss problems when testing their flash files from their local machines.
Problems can occur when your local file is trying to access / load content from the internet or another remote location. By default, flash is locked down to only talk to files in it's own "zone", and to make matters worse, unless you are running a debug version of the flash player, it won't necessarilry even tell you that a security error has occured, and just fail silently.
Below are the steps required to ensure local testing goes smoothly:
1. If possible, centralise your flash projects into a top level folder. Something like: c:\dev\ 2. Set your security preferences for the flash player to allow communication from local and internet zones. This is achieved through the flash player settings manager, located here: http://www.macromedia.com/support/documentation/en/flashplayer/help/settings_manager04.html 3. Add the folder above to the allowed folder locations. All subfolders under that location will also be given access to the internet. Add any additional location which you know you want flash to have full access.
Note - I belive you only have to do the settings change once and it will affect BOTH IE and FF plugins.