Hi Scampy
You say when testing with PIC, SDA and CLK lines are taken low when BV4611 is connected. According to the data sheet this will cause the BV4611 to start up in SERIAL mode. Have you set the PIC to pull SDA & CLK LOW or are they HIGH untill you connect the BV4611? Do you have the PIC start up with SDA & SCK as inputs untill the BV4611 starts up?
Surely SDA and SCK should idle HIGH.
Phil
By the way I'm in the UK