atmegatron's worked for me too..
I attached a photo with the one I removed.
I'm having relatively the same issue...
Without the ethernet shield my mega 2560 works fine but when it's plugged in the mega won't run any sketch and I can't upload one.
If I try to upload a sketch with the shield connected I get this error:
avrdude: stk500v2_getsync(): timeout communicating with programmer
My shield looks like this:
Should I remove the brown capacitor right beside the reset switch?
removing the capacitor worked for me too!, thanks
I have the same issue as reported here and same Ethernet shield as nephtyz. Did the removal of the capacitor nearest the reset button in the image from 20th Dec 2015 solve the issue?
I removed the Cap nearest the reset switch and my problems were solved.
Thanks a lot, much frustration will now be avoided
nymrod:
I have the same issue as reported here and same Ethernet shield as nephtyz. Did the removal of the capacitor nearest the reset button in the image from 20th Dec 2015 solve the issue?
I have the same board , and same problem, did removing the (only) capacitor next to reset work?
broko1:
I have the same board , and same problem, did removing the (only) capacitor next to reset work?
Hi everybody.
Quick solution that worked for me: cut (or bend out) the reset pin from the ethernet shield. No solder, no capacitor, nothing
Now the long story:
I had the ethernet shield working fine on an Arduino nano, with only the minimum connections made with jump wires. When I migrated to a Arduino Mega 2560 (I needed more RAM), and mounted the shield over, I couldn't flash it anymore. I did read the forums and the like, but I wasn't sure which capacitor to remove, nor the manual reset trick worked for me.
So, in a short motorcycle ride, I realized that the shield worked on the nano without the reset connected. Thus I removed that pin and start uploading sketches happily.
Good luck!
acerbus:
Hi everybody.Quick solution that worked for me: cut (or bend out) the reset pin from the ethernet shield. No solder, no capacitor, nothing
Now the long story:
I had the ethernet shield working fine on an Arduino nano, with only the minimum connections made with jump wires. When I migrated to a Arduino Mega 2560 (I needed more RAM), and mounted the shield over, I couldn't flash it anymore. I did read the forums and the like, but I wasn't sure which capacitor to remove, nor the manual reset trick worked for me.
So, in a short motorcycle ride, I realized that the shield worked on the nano without the reset connected. Thus I removed that pin and start uploading sketches happily.Good luck!
Thanks, but this didn't work for me 
I have the same problem. After speaking with the online shop "tuelectronica" (Arduino Ethernet Shield - TuElectronica.es) I have noticed that the shield use the com port, so that it is imposible use the serial to comunicate the pc and the Arduino Uno. It is posible with Mega for instance, there are 3 serial.
The solution of the shop ist load the sketch without the shield and after put it and all the code will work. The problem is that in the code it is not posible use serial.print or serial.write or any other funtion with serial. Neither the serial monitor.
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I had this same problem except with the Motor Shield V2.3 and it turns out that I must have used too much solder when soldering the headers to the shield because two pins were shorted together. I wasnt able to see the short because the stacking headers cover the solder joint visible from the top of the board but as a last resort I bent the headers to reveal the solder joints and then used solder wick to remove the short. Such as dumb mistake but I'm relieved that I found the short because none of the other suggestions worked for me.
Bad Soldering (of ICSP) pins to SSD's socket, made shield (and arduino) go crazy. Same error on 2 different ethernet shields.
Removed bad soldering and voila! problem solved!!
masterfull:
Bad Soldering (of ICSP) pins to SSD's socket, made shield (and arduino) go crazy. Same error on 2 different ethernet shields.Removed bad soldering and voila! problem solved!!
Thanks!!! the final attempt, the BEST...
I had exactly the same issue as everyone here. No trick helped until the last one - cleaning the bad quality soldering! I just scratch the "show circuit" out with a needle and bing - it started to work immediately!
Several hours of my live wasted on trying to figure out what it was till I found this forum.
THANK YOU ALL!
jurs:
- power off
- remove the shield from the Arduino
- power on
- then load the example sketch "BareMinimum" or "Blink" to the Arduino
- power off
- then put the Ethernet shield back again on the Arduino
- power on
And always make sure, that there must be a little distance between the USB connector on the Arduino and the soldering side of the Ethernet shield: Do not create a short circuit with the shield and the USB connector on the Arduino board!
THANK YOU SO MUCH.
The short circuiting part really helped 
@keson: That was it - thank you so much!
Thanks!
Same for me on a Hanrun ethernet shield
Pin 5 (Reset) was shorted to the SD card shield with poor quality soldering
FYI pin 6 is ground
The same issue for me with HanRun HR911105A 15/10 Ethernet Shield.
The solution: remove short-circuit near the SD slot shield. !!! Thanks a lot guys!!
Hi all,
VERY old topic, but for reference I write here my issue (seems very old issue with new Hanrun HR911105A 17/20 as well).
I got my ethernet shield a weak ago (November 2017).
- Arduino UNO works nicely alone (blink test, etc.).
- Arduino Wiznet W5100 ethernet shield works as well (SPI side IP, ping, http server test).
BUT I could upload sketches ONLY when ethernet shield is removed otherwise uploader just complained "avrdude: stk500_getsync(): not in sync: resp=0x00".
The solution was EXACTLY the same as Atmegaron (post #5 in this thread) suggested: removing a small capacitor from the reset line (from next to the reset button in ethernet shield).
It is VERY interesting that the problem was the same as 5 years ago.
There is nothing new under the sun..
BTW my config:
- Acer laptop, Ubuntu 16.10, USB2, USB3 (both works nicely).
- Arduino UNO (1 week old) - with mini USB port - power consumption is minimal - from eBay
- Ethernet shield (Wiznet W5100 chip) Hanrun 17/20 - power consumtion is 150-160mA (190 mA during reset/startup) - from eBay
Removing the capacitor worked for me. I could not upload a sketch with the board attached until I removed it. I bought this board several years ago and pulled several off the shelf and none of that batch worked until I removed the capacitor. Thanks.