R – Mixing Flash and Flex-compiled ActionScript code through a runtime shared library

we are two people working on a Flash application.

I work on some ActionScript 3 code,
which I compile to a .swc file using the Flex SDK on Linux.
My colleague uses the file as a library for his .fla file in the Flash IDE,
uses my code in his scripts, creates MovieClip and Sound objects
with the classes it provides,
and builds the final .swf file from there,
with everything linked in.

We would like to link the flex-compiled code as a runtime shared library,
so I can substitute a new version of my classes and see the result
without going through the Flash IDE.

Is what we're trying to achieve possible?
If so, any idea what we might be doing wrong?
(see below)

We use the Flex SDK version 3.4.0.9271 and Flash CS4 10.0.2.

Using the .swc as a static library works fine.
However, as soon as we move it
from the "Library path" tab
to the "External library path" tab
in the "ActionScript 3.0 advanced settings",
the applet stops working.
We have also tried to specify a URL for the .swc file
in the "Shared library properties" from the "Library" window,
with no effect.

(Please forgive the back-translated menu names,
feel free to correct me.)

The ActionScript code is compiled with the following command-line
(there are classes from three other packages):

acompc -output=engine.swc -compiler.source-path=.
       -include-classes=lib.room.TransientLoc,lib.room.State,...

Thanks for any suggestion in advance,