new UNO fault code avrdude: stk500_recv(): programmer is not responding prob

Hi hope you can help....

Just purchased a new uno.

First time user.

Loaded upto date software onto a mac book pro running 10.5.8

followed all the points re set up

Copied and verified the code for the blinking led

keep getting fault code avrdude: stk500_recv(): programmer is not responding

Cant find any leads on the forum and sites to help

Tried on another mac running 10.5.8 and no probs

Also keep getting the usb device unplugged window/warning when disconnecting on my pro not the other!

Hope you can help

screen shot attached of IDE message serial port and board settings