Kidlet has just been updated and should be working now. If you have the channel installed, you should be upgraded automatically within the next 24 hours. If you want to force an update, simply go to the Channel Store.
If your box is on the latest firmware, then it sounds like it might be worth a call to support for you. It might be something unusual with the state of your box. Hate to sound too Microsoft about it, but did you try rebooting? (unplugging/replugging the Roku's power cord.)
yes, my box has the latest firmware and everything is working great... I might be going crazy here but I can't watch any episode directly from their website using my PC and the Kidlet channel on the Roku box still isn't working for me.