[CentOS] CentOS 5.4 x86_64 and HPLIP-3.9.12

I recently purchased a HP Officejet Pro 8500 (A909a) and it's ethernet 
attached.  It's been configured and works perfectly from WinXP, Win Vista, 
Windows 7, and Fedora 11 x86_64. However, on my machine running CentOS 5.4 
x86_64 I can't get the configuration to work so that it prints duplex 
(2-sided).  The HP Setup appears to be working from the command line, but 
the graphic portion doesn't appear to work. Any ideas?

TIA,
Gene Poole
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