User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:2.0b1) Gecko/20100628 Firefox/4.0b1 Build Identifier: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:2.0b1) Gecko/20100628 Firefox/4.0b1 The issue is that if I run 64-bit Firefox 4.0b1 then certain plugins, such as Flash, which are 32-bit will not load. With the OOPP approach it may be useful to include support for allowing 32-bit plugins to run in a 32-bit sub-process when its 64-bit equivalent is not available. I imagine this would be possible with this new architecture? I am not sure whether we should treat this as a feature request or a bug, so I will let the developers decide. In many ways it is a feature request, but the behaviour may appear as a bug to many general users. Reproducible: Always