This doesn't arise too often for GarageBand users, from what I have been able to research, but there are definitely many discussions about this particular error message, the "disk is too slow" error, that you can find online.

Unfortunately I haven't found any definitive answer about why you might suddenly see this after working for days, weeks or even months on your computer with the very same type of projects.

In fact, search for that error message in the GarageBand built-in help, and there are zero matches. Not so useful!

So first, here's the error I bet you're seeing:

Familiar error window? Ayup, "Core Audio: Disk is too slow (Write): (-10002)".

Generally, you can fix this by restarting your system, but there are also some tips I found to help avoid this message in the future:

1. Quit as many other programs as you possibly can. Freeing up system resources can often help with disk swapping problems, too little RAM, and so on.

2. Make sure you're plugged in and that you don't have any strange Energy Saver settings (go into System Preferences to check it out). The one to avoid? "Put the hard disk(s) to sleep when possible."

3. Don't work with source material that's directly on an audio CD or DVD: copy it onto your computer drive before you go further.

4. Make sure you don't have FileVault running. Don't know what that is? It's a built-in disk security system that keeps your data encrypted but slows down reads and writes because everything has to be encrypted/decrypted on the fly.

Here's how to check if you have that running: Go to System Preferences and look for the "Security" icon on the Personal row:

Choose it, then click on the "FileVault" tab:

On mine you can see "Turn On FileVault". If yours says "Turn Off..." well, then you should seriously consider turning it off as it will speed up disk writes on your computer.

If those don't do it, you might well have a problem with your disk or computer. For most people, however, these should take care of the problem so you can get back to mixing and producing your material in GarageBand.