You can load
.75 on your duemilanove, then put the duemilanove chip in the guino and see if that brings it back to life.
Then try to reclaim the chip that was in the mpguino by putting it in the duemilanove.
Note, I've made a few changes for reliabilities sake since you got yours (including removing the bootloader). If you want to send in the old mpguino chip I can reflash just that too.