I have a component that I originally created in vanilla MX, gave it to a client to use (he used it in MX 2004 and made changes to it). Now when I try using it in MX the application immediately quits to the desktop. Is there anything I can do to get the component working again? Is this a known issue?

MX 2002 uses v1 components architecture method and MX 2004 uses v2 components architecture method. The v2 components were written to comply with several web standards (regarding events, styles, getter/setter policies, and so on) and are very different from their v1 counterparts that were
released with Macromedia Flash MX and in the DRKs that were released before Macromedia
Flash MX 2004. V2 components have different APIs and were written in ActionScript 2.
Therefore, using v1 and v2 components together in an application can cause unpredictable
behavior.

If you would like to update your applications to work when published for Flash Player 7, you must convert your code to use strict data-typing. For more information, see ?Creating Classes with ActionScript 2? in ActionScript Dictionary Help.

(Some of the above resources are from macromedia's Flash MX 2004 Help PDF files)

author: Chinese Boy

It's not that...

He nowhere says the guy who edited the file in MX2004 replaced the
components with V2 components, never says he used components at all.

What can be done is make sure the guy who edited the FLA saved it as a MX
document (Save as... pick MX format, not MX2004 format).

If this is no worky I suppose you'll have to grab the latest 2004 demo and
quickly examine where the cause may be, until MX opens the file ok (try
removing or altering stuff from within MX2004 and resave each time in MX
formaT).