I was having issues with the bus freezing up .. slaves holding SDL low.. so I...

I was having issues with the bus freezing up .. slaves holding SDL low.. so I rewrote a good portion of the interrupt logic based on the application notes from Atmel.  One major improvement is using the RXNACK flag in the STATUS register, which indicates that no device responded to an address packet. Assuming that the chip will always give an interrupt status, I believe it's possible to eliminate the timer as well.