We’re aware of this problem, which is specific to Leopard. Apparently Apple decided that its previously supported method for loading sound banks in Tiger should just crash in Leopard. I’m still investigating a workaround. Sorry for the inconvenience.
Thank you very much for your prompt answer. We have created our own sound bank because the quality of the sound of the Quicktime DLS is not so great for ear training purposes. I hope there will be a solution to this issue soon.