rosserial_python: Serial port read failure

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I have followed the tutorials for setting up the Arduino IDE and loaded the Hello World sketch to my Arduino.

When I run: rosrun rosserial_python serial_node.py /dev/ttyUSB0, I get:
[WARN] [WallTime: 1461761129.635609] Serial Port read failure:
[INFO] [WallTime: 1461761129.636331] Packet Failed : Failed to read msg data
[INFO] [WallTime: 1461761129.636872] msg len is 8
[WARN] [WallTime: 1461761129.653651] Serial Port read returned short (expected 74 bytes, received 58 instead).

This had previously worked. Since then, I have installed catkin and did the Simple Publisher and Subscriber tutorial so that probably affected something with the ROS Arduino setup.

I am using Ubuntu 14.04 with ROS Indigo and arduino-1.6.8 and would appreciate any suggestions for tracking down the problem.