Mark,
I've already sent you the MPEG plugin that I use. Here is a small MPEG movie (pretty funny, by the way) you can use for testing. Try this:
MPEGFile primFileValidMPEG: 'chimp.mpg'
If this returns true, then the module has loaded successfully. Remember, the MPEG plugin must be in the same folder as whatever VM you are running.
To be certain that you are running a particular VM (if you have a lot of VM's on your disk, as I do), you can create an alias for the VM and start Squeak by dropping the image file onto that alias.
If the module is loaded, then:
Smalltalk listLoadedModules
should return a list than includes:
'Mpeg3Plugin 9 November 2000 (e)'
It's remotely possible that the module is not loading due to insufficient C heap space. To reserve extra heap space, you can execute:
Smalltalk extraVMMemory: 100000
then *save that image* and restart it. You have to restart because the C memory reservation is done at image startup time, before the memory has been given to Squeak.
And, in case you missed John Mac's message, note that the plugin is sensitive to the case of the file name extension. It will reject a valid MPEG file named "foo.MPG" but accept one named "foo.mpg".
If none of this works, please let us know what version of the Squeak VM and of Mac OS you are using. But I'm hoping that the plugin was simply not in the VM folder.
One more thing to try--can you load other external plugins, such as the JPEG plugin?
-- John