Ok Flash and Linux is pain. Real pain. Turned out that I've found another combination to get this working.
FYI the system is Debian/unstable (currently more or less equal to what will be Squeeze) with Linux 2.6.36 running Fluxbox as the window manager on an P4 3.6Ghz (yes old, 32bit hardware) with an Intel on board graphic ship 82945G.
So to get this working I've to
a) Start the game in fullscreen - otherwise link cursor is shown but left button clicks have no result.
b) Lunch a game.
c) Turn of fullscreen
d) Select in the flash player menu a quality of medium or low
e) Select from the flash menu (remember limitation of a) ...) to go back to fullscreen
=> enjoy the game without the cursor f'cking up everything
It's a bit of a pity that you created such a lovely game with such suboptimal tools but at least I found a somewhat strange way to work around the problems.
Now I just need to find out what todo after falling of the bridge ...
Thanks for all the tipps here, made it a bit of an off-game bonus level with hints *g*