imac 10.9.5 avrdude programmer not responding now

I've been using my Arduino Duemilanove on my imac for years. I just update the OS to 10.9.5 and I'm getting the avrdude error. I fixed this on the last update by installing virtual FTDI drivers. This is not working now. Any suggestions?

I just noticed the chip I was using is the atmega328-pu. This is not working with my duemilanove

I then tried the atmegaP328-pu and this works. What's the difference? Can I fix this?