Are you using a Carbon version of Helios? There aren't many of those posted (most are Cocoa), but I think the SDK distro is still offered in Carbon flavor.
If that alone doesn't help, try looking for your error in these tables:
Though FB4 Plug-in is not exactly a CS5 app, it uses CS5 install/licensing libraries, so the same solutions would probably apply.
I forgot to mention I am using the Carbon Distro... In the end after a day of trying and general weird behaviour (even from the standalome install which just kept asking me to install a disk!) and a gloating co worker for whom it went on first time... I rebooted my mac and wadda ya know....one installed plug in.
Sometimes you just have to accept, your computer needs to make monkey out of you for things to work correctly
I'm having the same issue, running OSX: 10.6.6 and Eclipse Ganymede. I installed the plugin a couple times, but still getting the Configuration Error - Error 6.
Thanks a lot in advance!