Hi All,
the same problem - after loading example R01_Logo it was impossible to load any sketch via IDE (1.5.6-r2).
I just tried the procedure described at http://arduino.cc/en/Main/Robot
Because of the way the Robot handles reset it's best to let the Arduino software try to initiate the reset before uploading, especially if you are in the habit of pressing the reset button before uploading on other boards. If the software can't reset the board you can always start the bootloader by double-pressing the reset button on the board. A single press on the reset will restart the user sketch, a double press will initiate the bootloader.
So I pressed RESET button twice between Compiling and Uploading phase and new sketch was loaded via IDE as usual.
I wanted to apply the procedures described earlier with AVRISPMKII programmer but it wasn't necessary.
Hopefully it helps someone.