I'm having the same problem
Running a MacBook Pro 10.5.8 2.53 GHz Intel Core 2 Duo with 4 GB 1067 MHz DDR3. 1.89 GB available.
I'll set up garageband, will be recording just fine and at some point while working slides in keynote it stops recording. Of course I don't get to see this until I'm done with Keynote and the presentation is finished.
When I return to garageband, the playhead is still moving forward, even though the waveform and actual recording ceased some 40 mins back. There is no warning or message indicating why recording has stopped.
In the last week I have received messages about scratch disk being near full. Which has lead me to close unnecessary programs, clear the desktop items and restart. Although this message did not come up when this problem has arisen before, but only around the same time as the most recent.
Any advice on what to do to ensure garageband keeps recording? Record directly to an external HD? Clear up more hard drive space on my machine? Get a more basic audio recording software that doesn't hog as much memory?
Please help