asterisk users - May 2007 - Cutted audio or 2/3s blanks on EuroISDN - Asterisk 1.4

Morning all,

we face a strange problem on a dual Xeon server with 2 GB RAM and 2 
B410P cards. On ISDN calls, audio is sometimes poor (micro 
cutted/scratched) even cutted during few seconds (2 or 3). Problem 
appears only on some calls and isn't reproducable.

Kernel is a Debian/Etch 2.6.17-4 amd64. We are using misdn1.1.2 with:

Asterisk SVN-branch-1.4-r62218 built by root @ SrvPhone on a x86_64 
running Linux on 2007-05-05 13:42:13 UTC

Cards are setted in TE-PTP mode, 7 of the 8 ports are used. Telco is 
Belgacom - Belgium. They checked lines and tell they are ok.

Thanks for any hint.

-- 
Daniel