I accidentaly powered my Arduino Uno with 24V through the 5V pin, like shown in this picture:
After that, I noticed that it was drawing more than 100mA even though I had nothing connected to it. I checked with my meter and there was a resistance of around 60 ohm between 5V and GND (even without the atmega inserted in the socket). When I power it, the capacitor C1 in the Arduino Uno schematics (http://brittonkerin.com/annotateduino/arduino-uno-schematic.png - C1 is in the upper left corner), which in the board is right next to the 3V3 regulator, gets very hot. When I try to upload a sketch, I get this error: avrdude: verification error, first mismatch at byte 0x0000 0xff != 0x0c avrdude: verification error; content mismatch. If anyone knows what is causing this, please let me know. Thanks!