Ralph,
maybe i'm the ony one or my computer miss some internet plug-in, but i can't see your schematic... are you using P82B96 or any other Philips in the PCA951X family?

I ask you that because my next design (on wich i'll probably spend ... few months maybe a year on), i'll have to deal with around 100 (maybe more) of those hot-swap I2C buffer to protect the main frame while the user change/add/swap control slots/modules.

Sorry Robert to be off topic