I tried the new Red upgrade 4.2 to be able to use it into Premiere Pro Cs3.1.1 (Mac 10.4.11) but it can be done - when the installer starts, it indicates that it needs a future version of PP to validate the install into it !...
Is there any another way to install it and to use Red as a PP plug-in?...
Upon rereading the title of your message, I noticed that you are using a Mac. Unfortunately at this time we do not have a solution for Boris RED users in the Adobe Premiere Pro CS3 host on the Mac. I believe it should work on Windows, although if you're on a Mac that won't help you all that much.
Premiere Pro CS3 is new to the Mac and there are many integration issues that have to be worked through before RED 4 will actually function as expected. When we have an update of RED 4 that works within this PP CS3 on the Mac we'll post a message on the web site and also on the Cow forum.
Meanwhile please know that you can use the BCC 5 filters in Premiere Pro CS3 on the Mac.