maddening myst4 technical glitch renders game inoperable

The system: iMac Intel, running Tiger 10.4.7

The problem: cannot launch Myst4.

Attempted solution: the "chmod a+x Myst4" tweak suggested on Ubisoft
forum. I also tried this with a lowercase "m" thinking that that was
probably what I should be doing given that both myst4.app and the unix
executable file within its package had names that started with a lower
case "m". Tried it both ways.

The result: nothing. The screen goes black, then blue, changes its
display size, then crashes and immediately loads my screensaver
instead. I cannot play Myst4 on my Mactel system at all. It works fine
on my PPC at work though. It seems that the problem is that the unix
executable file is trying to execute a command and is being forbidden
to do this, has noplace else to go from there and just stops. There's
no good reason why Myst4, if it is a properly written PPC game,
shouldn't run under Rosetta, and it sure looks like this tweak above
has worked for some, suggesting that *some* sort of tweak will work for
me. I have to rely on fora because Ubisoft simply blows people off
saying that they must use the required system, and Apple blows people
off saying it would work under Rosetta if properly written.

Grrrr!
And naturally, I have no inclination to purchase Myst5 until I am
satisfied that I can get these damn things to load in the first place.
Of all the Myst games I have, the only one that works now is realMyst
(this is just venting--I recognize that this is a Mactel absence of
Classic issue as to Riven and Myst3:Exile).
Double grrr!