I've experienced an odd problem that is either related to or caused by optiboot. Background first:
Board: design based on Duemilanove, except w/3 added I2C devices: 18-bit ADC, 512K EEPROM, temperature sensor
USB-serial converter: FT232RL
MCU: DIP ATmega328P-PU, 16MHz (crystal)
bootloader: optiboot (Oct. 2011 -- current version AFAIK)
Arduino version 0022
Windows XP
I've built and tested a couple dozen of these boards that work fine. Today, and on one previous occasion, a newly built board accepts a new sketch uploaded from the IDE via USB, but then does not launch the sketch. Instead it remains in a reset (i.e. does nothing) state. I've checked the reset pin and it is high.
The chip will immediately begin to execute the new sketch when either the reset button is pressed or if the power is toggled. But it will not launch a new sketch (or even the previous sketch) immediately after uploading.
I reloaded optiboot into the chip at least four different times, in three different ways (arduinoISP over ICSP cable, optiloader over ICSP cable, and arduinoISP to chip in zif socket). Exact same behavior.
So I tried burning the old Duemilanove bootloader into the chip, and the problem went away. The "failure to launch" problem did not occur with the 2009 bootloader. And then when I reburned optiboot into the same chip, the problem did not occur again.
The problem is fixed for this board and this chip. But it has happened to me twice now so I can't just chalk it up to a bad ATmega chip.
Any ideas where the problem lies?
Jim