There is some problem with scripts on the page during flash initialization in case if fileUpload was added to the page by ajax request.
But we have workaround.
Please add this to your page to solve the problem:
I am having the same problem - my rich:upload is in a section of page that is dynamically rendered. The Add button is not working (does not popup file dialog) in FF or IE7 when I use allowFlash="true", it works fine when set to "false".
I tried pasting your workaround into my page just before the rich:upload but it does not seem to be working. Is there more to this workaround that I am missing?
You should paste this not in the included dynamically page, but somewhere out of it.