asterisk users - May 2004 - "skipping" / dropped audio, high-pitched squeal on X100P channels..

This is driving me nuts.  Any help appreciated.

I have a couple of annoying problems in my Asterisk box, and I'll be 
dipped if I can figure them out.  The box in question is an Asterisk 
CVS-05/03/04 (1.0) checkout, using the Zaptel drivers of the same 
vintage from CVS.  There are two X100P cards, and one TDM400P with a 
single FXS module.  The machine is an Athlon 2400XP CPU, Debian 
"unstable" running Linux 2.4.26.

The first, and more pressing problem, is this audio gremlin I have on 
my X100P channels.  The problem exists on both.  One is plugged in to a 
normal POTS line, the other is connected to a Packet8 ATA.  The call 
will progress normally, and then a loud "ringing" sound will be heard 
for about 2 seconds, drowning out the audio.  The calling party does 
not hear the sound.  An example, caught in a voice mail message, can be 
heard at http://voip.feedle.net/msg0000.wav.

The second problem, and it is mentioned only because I think that it 
might be related, is infrequently (on both analog and SIP phones) 
Asterisk will "skip" about 2 seconds of audio.  This problem is not as
predictable, and not nearly as annoying as the above audio problem.

Any help appreciated.. I can't figure out why this is happening for the 
life of me.