It's a memory error - could be the memory module or the socket.
Unplug the system, remove the battery and hold the power button for 30 sec. Remove and reinstall the memory module (service manual link below). That may fix the problem.
If it doesn't, since there's only one module, you'll need to replace it with a new one. If that doesn't solve the problem, it's the memory socket that's bad - in that case you're probably better off replacing the system, as this is a relatively old model and the mainboard isn't going to be inexpensive to replace.