A newer version of avrdude includes configuration settings for the 1284P. I have 5.10. Arduino ships with 5.4.You may be able to just "upgrade" the avrdude.conf file. I've attached the version from my computer.
Now to push my luck a bit... Would you have a HEX file for a bootloader that clocks at 16 MHz? I thought i found one but I can't seem to get it to work :-(
I know this should be an wasy error to find int eh conf file, but line 320 looks fine to me, nd I retyped it to make sure there were no hidden characters. Here is the error avrdude spits out through the IDE:Binary sketch size: 450 bytes (of a 32256 byte maximum)error at C:\Users\jim\Desktop\arduino-0022\hardware/tools/avr/etc/avrdude.conf:320 unrecognized character: "a"