Error frames

Hi,

I’m getting following error after which the asterisk crashes.

Mar 12 13:16:51 WARNING[16934]: file.c:587 ast_readaudio_callback: Failed to write frame
Mar 12 13:16:51 WARNING[16934]: file.c:587 ast_readaudio_callback: Failed to write frame

pleaes let me know what could be the reason

asterisk 1.14
zaptel 1.12 with ztdummy as time device.Set kernel timer 1000

regards
rudra