I'm trying to get the ambiance plug to work with Cubase. i'm running osx 10.4.5. the plug is in the vst plugins folder, but it shows as a "unix executable file" and it's not showing up in cubase. It showed in protools and worked very poorly as a vst wrapped rtas plug, but now in cubase it doesn't even show up.
Hmmm.. sounds like something went wrong when unstuffing the file. Is this the demo version or a registered version? (I just re-downloaded the demo, and it unstuffs just fine). You don't say which version of Cubase you have, but SX3 includes a reverb, called "Roomworks", which is in fact a re-skinned version of Ambience, licenced to Steinberg.
Anyways, if you have a file utility such as File Buddy, File Xaminer, or even Super Get Info, you may be able to correct the existing file by changing its type to "aPcs" and its creator to "stCA".