I had a little more time to dig into the data sheet and can see where you got address 3a and 3b from. It is the result of adding the r/w bit to the 7 bit address. From looking at the I2C code I wonder if it twittles that read write bit for you. I wonder if the address they are really looking for there is 0x1D.

If you want to work this out off line my email address is k9wis@yahoo.com

Brian