Basically, plug-ins for Intel Macs on OS X need to be published specifically to be compatible since the old system was passed up for the FX plug architecture. Some developers have updated their plug-ins and some have not. There is nothing you can do to make them compatible except get a old power mac.
How about importing the project into a CS3 one and saving it? Or perhaps find someone to save in 6.5 then 7 then CS3 maybe the funky code will clear up.