Quote Originally Posted by squirrel View Post
... i also get the same freezing once in a while, except the LCD starts blinking, probe moves in time with the blinks, if that makes any sense and then the whole thing resets and i have to do the trick to get the SD working all over again, which involves powering off, plugging the usb back in, checking on the LCD that it reads the card, turning the power on and quickly unplugging the usb as sometimes it resets shortly after powering on with the usb plugged in, which in turn resets the SD card, somehow...
Sure sounds like the 5V from the MEGA2560 board could be dropping out. Do you have another USB cable/computer to try or a powered USB hub to feed the USB through? Maybe the USB port on the computer you're using can't handle the additional load of the servo running; if it drops out the 5V regulator on the MEGA2560 board certainly can't handle the added servo load for long.