asterisk users - May 2005 - chan_oss.c:572 oss_write: Unable to set device to input mode error

hi 

i'm a newbie in asterisk...i installed asterisk but when i tried to
dial 1000 for the first time i got the following error messages and i
don't hear anything...

May 29 20:46:03 WARNING[262160]: chan_oss.c:413 soundcard_setinput:
Unable to re-open DSP device: Device or resource busy
May 29 20:46:03 WARNING[262160]: chan_oss.c:572 oss_write: Unable to
set device to input mode
May 29 20:46:03 WARNING[262160]: file.c:550 ast_readaudio_callback:
Failed to write frame
    -- Playing 'demo-congrats' (language 'en')
  == Spawn extension (default, s, 5) exited non-zero on 'OSS/dsp'
 << Hangup on console >>

can any one please help me out with this problem??i'm using redhat 9.0
on IBM T41 with AC'97 sound card...

thanks in advance
emon