Lego Mindstorms RCX Brick

For future reference, if you are using Lego Mindstorms and BricxCC is generating a "Compile failed. No (or invalid) reply from RCX." error when you try to download a program onto the RCX brick, try re-downloading the firmware onto the Brick.

You can find out how to do it here:
http://www.kipr.org/curriculum/power.html

The firmware can be found in the SDK here:
http://mindstorms.lego.com/sdk2