Could be this will help:

Find a proper aux. power supply for the UNO and plug it in. 

Gently tap the reset button on the Uno if needed.

Could be this will help:

Find a proper aux. power supply for the UNO and plug it in. 

Gently tap the reset button on the Uno if needed.

Bill does have a point, it could be that the USB port can't provide enough power for the servo.

I googled that error message and it suggests that there is an issue with the installation of your drivers for the comm port.

Check that you've selected the right comm port in the IDE and check that you've selected the Arduino Duemilanove from the menu too.

Alright, I will give that a try.

Thank you!

Hey Andy,

Thanks for your reply. I am new to the whole Mac environment as well, so I am trying to get that all worked out. However, I have tried this on a couple of machines that I have used the Arduino IDE on, that run Windows and it does it on them too.

Let me describe the problem in a little more detail. I can program the arduino just fine and run it without any issues, until I hook up the servo. So I upload the servo code before anything is hooked up(it uploads just fine) and then wire up the servo while the arduino is unplugged. When I plug the arduino in, the servo moves slightly, then stops, the lights on the arduino flash. I let it run last night after posting this, and what happens is it will move slightly forward, stop reset, and repeat until it reaches 180deg then it moves back to 0deg in all one motion.

I didn't let my arduino get to that point before out of fear of hurting it somehow. I am fairly sure that the servo's behavior is not consistent with the code. The servo is a 4.8V to 6V servo, could that mean anything?

Thank you again!

I looked on a distributor's web site for mA spec on your servo and they did not provide it.

Option: try changing all delay(15) to delay(20)

Watch a video: http://www.youtube.com/watch?v=jVZJy6OlwcA

Read about other's experiences at the Source.

More fun: http://playground.arduino.cc/Learning/SingleServoExample

This site suggests it takes 200mA

http://saigon-hobby.com/products/649-servo-emax-es08ma.aspx

The max. current output from one pin is about 40 mA.  If the servo is UNLOADED then it might move smoothly under control of the program and only draw about 20 mA.  That may or may not prove a useful point of data to you.

A STANDARD HOBBY SERVO as sold by adafruit.com has these Technical Details: 

• Power: 4.8V - 6V DC max (5V works well)
• Average Speed:  0.2sec/60degree (@ 4.8V), 0.16sec/60degree (@ 6V)
• Weight: 39g (1.37 oz)
• Torque: At 5V, 5.5kg-cm / 76oz-in, and at 6V 6.5kg-cm / 90oz-in.
• Size mm: (L x W x H) 40 x 20.0 x 38 mm
• Size in: (L x W x H) 1.60x.79x1.50

On the other hand Your Type:     EMAX ES08MA   (means Extra Sensitive 08  Metal Analog)

Size:     32 x 11.5 x 24 mm(1.25 x .45 x .94in)

Weight:     12g / 0.42oz

Operating voltage:     4.8V~6.0V

Operating current:     200mA/60º

Operating speed:     0.12sec/60º at 4.8V; 0.10sec/60º at 6V

Stall torque:     1.5/1.8 kg.cm 20.8/24.9 oz.in (4.8V/6v)

Dead band:     1-2 uSec

Gear Material:     Metal

Connector wire length:     25 cm

Connector type: Futaba/JR compatible

So now we see that compared to a Standard Hobby Servo the EMAX ES08MA is a light weight wimpy EMO kind of servo designed for use in fly weight carbon fiber egg beaters. 

Q. What signal do servos require to operate?

A. All Hitec servos require a 3-4V peak to peak square wave pulse. Pulse duration is from 0.9ms to 2.1ms with 1.5ms as center. The pulse refreshes at 50Hz (20ms).       SOURCE

All you have to do is modify your HW interface and the Arduino Sweep Example Code to generate the kind of signal your ES08MA was designed for.  That would be found in a detailed data sheet from the OEM.  Link to be provided by a reseller.  I will say this: the delay(15);  statments can be changed to delay(5); since it is extra sensitive - meaning quick to respond.  Also the new generation of servos have high impedance control inputs (think CMOS op-amp) and require next to no current (as in 0.0 mA) flowing into the device on the PWM control wire.  For starters, since the 'Duino's output square wave is 5 volts you will need to put a voltage divider (a pair of resistors in series where the desired voltage level is found at the node between R1 and R2 where R2 >= 2*R1 and R1+R2 > 500 ohms) in place to reduce that peak level down to ~3.5 volts.

Wow, thank you for such a detailed answer. This helps a ton. I will do this, and get back to you guys and let you know.

I would be the one who would buy weak servos. To be honest, I didn't know these were tiny servos. Oh well, I will have to buy normal sized ones!

Thanks again for your help!

Sure.  You are welcome.  If you can run the HW mode with a voltage divider, we would be very interested to know if that alone resolves the issue of poor performance.  So the set up would be as follows:

connect R1 from pin 9 to servo control wire and

connect R2 from servo control wire to ground.

FYI, Harbor Freight has a $4 digital multimeter this week in the USA.

Found a video for you that covers the 'Duino Sweep demo.