Corrupt Audio. 2.4a2 OS X

I’ve been messing with audio syncing and it mostly works fine but every so often the audio playback corrupts (to a high-pitch squeal) and I have to save>reopen-last to get it back to normal.

Anyone else suffered this or anyone know if it’s a known bug?

Mac G4 (2003)
OS X (10.3.9)
ATI, (RV250??)

Don’t know where to find sound card info but it’s whatever shipped with the machine.

Blender 2.4a2, 10.3.9, PY2.3