asterisk users - Mar 2004 - Buzzing X100P - call 650.210.9331 to hear it

Can anyone tell me what that strange buzzing sound is?

My system is working fine except for this problem with the X100P. After 
what seems to be a random amount of time after system startup - 
sometimes hours, sometimes days, the card gets bolloxed and just does 
that buzzing sound when the line picks up.

Restarting asterisk or re-running ztcfg does not make it go away. I 
have to reboot.

Thanks,

Sean