Hi,
I am using an Wifi Shield (http://store.arduino.cc/product/A000058) with an Arduino Mega. I have already updated the firmware. The leds are on and when i am uploading the code both leds DATA and LINK are blinking, but still i got the message WiFi shield not present. The codes that i have tested are from WiFi library and its called ScanNetworks. I have remove the jumper from the shield. In this link http://www.arduino.cc/en/Guide/ArduinoWiFiShield, i have found this sentence WARNING: If you use the solder jumper, do not connect the shield to a rev3 or later board. To be safe, remove the IOREF pin on the shield. Otherwise, you will be shorting 3.3V to 5V through the IOREF pin. Should i remove that pin as its too tiny to pull out? I have also using a 3g/gprs board from cooking hacks above, yet i do not think it would raise any issues.
I use a wifi shield with a Mega, and it works ok. My Mega is a pre-R3 version, so I use a jumper from 5v to the IOREF pin. Without it, I get the "WiFi shield not present" message. If you have a R3 Mega, you don't need the jumper.
I have also using a 3g/gprs board from cooking hacks above, yet i do not think it would raise any issues.
Have you tried it without this board?
yes i have tried without the 3g/gprs board. Unfortunately, my Arduino Mega is rev3.