Sync Error

Im trying to upload my program to my arduino uno r3 and i get this error

avrdude: stk500_getsync(): not in sync: resp=0x00

anyone know what i need to do to fix

When you plug in to USB, does you computer see the device?

I am having the same problem, but it says its conected to a COM 3 or something like that. I am using the USB cord, could that be a problem?

Coding Badly has a fantastic "Loop-Back" Test instruction that helps to isolate communications with the Atmega8u: http://arduino.cc/forum/index.php/topic,73748.0.html

I am starting to see an issue with Unos with the USB assigned virtual com-port 3. In the "old days", com1, com3 and com2, com4 were only seperated by IRQs (interrupts) . I have no troubles with my Uno on Com8.

Anybody have a clever way to exclude the Uno from Com1-Com4?