D-channel dropping down with all calls interrupted H-E-L-P!

I use asterisk for 2 years or more.

I have a euroisdn PRI coming into a wct4xxp (TE405P) card moreover I have a zhone channel bank.
spans 1 and 2 where configured for T1 and 3 and 4 for E1.
The arrangement has worked until October when we changed location.
At the new location the pbx was dropping about every 40 minutes (more or less). The pbx is connexted via an shdsl line.

I have now a replacement card from digium and everything happens with both cards. ( They thought at first that it was a hardware problem).

The problems happen with all versions ranging from 1.0.9 to 1.4.3 .
With older versions I had been able to reproduce the every 40 minutes drop of all the lines (that now it is felt that it was good) but with newer versions all the lines drop together every 3 minutes.

I have checked the line with another card I had (from PIKA technologies - with montecarlo drivers on a windows platform ) and everythink works normally.
I was able to keep the line up for more than 90 minutes playing a recorded message and hearing it from the other side.

If I define the T1 lines as spans 1-2 and the E1 lines as spans 3-4 the E1 line is unable to syncronize and goes into yellow alarm.
So I changed the configuration putting E1 lines first and after T1 in order to have the line to syncronize from the network.

I had been without phones for 10 or more days.

When absolutelly desparate I deeped into the code of asterisk zap.c and commented out the actions that happen when a zap channel receives an alarm, with this change the E1 doesn’t drop and the worst that happens is that for 3 or 4 seconds the calls may receive noise (the dchannel is lost and goes down and up again) but without dropping and restarting all the calls.

All sort or errors are involved “short write” “unable to retransmitt frame” FCS etc.

The same things happen using a new asterisk now installation and and trixbox.

I have changed also PC and checked for missed interrupts but nothing.

I know that is a syncronization problem and that the D-channel goes receives an alarm but I do not know how to resolve the problem.

While it is more than 3 weeks that I try heavilly to understand the problem I cannot understand it.