Roy--
Have you considered a hosted solution?
Also, I know it is not Open Source but I believe that MicroSoft Live Meeting may be able to accomplish your goals. I am not 100% certain.
My company provides conferencing services so if it is something you are interested in and what me to research for you in more detail, just let me know.
Also, if you do find an open source solution that meets your needs, please let me know what it is so I can research it further and see if it is someone I may want to partner with moving forward.
Good Luck
Thanks,
Jim Radtke
636-391-7738
jradtke@commalliancepartners.com