[Res'ed]PSTN incoming call RX problem (X100P, 1.2.1), echo?!

Following update to Asterisk 1.2.1 from 1.0.9, including Zaptel and Libpri, it appears my SOHO installation picked up a problem with the RX line on incoming calls via my single X100P clone card. I hear a lot of noise/static/cracking sounds. Caller hears me fine. ztmonitor shows a lot of signal: (Sorry, proportional font generates “off the chart” look)

( # = Audio Level * = Max Audio Hit )
<----------------(RX)----------------> <----------------(TX)---------------->

even though caller does not speak.

Interstingly, this is only for calls which I receive. Outgoing calls are fine. Which leads me to believe this is a problem regarding echo cancellation. It is turned on (zapta.conf), and I experimented with different values for echotraining, 200, 400, 800, 1000 to no avail, same for different rxgain levels from 0.0 to -15.0

I stopped at this point, I am in the dark here. Trying MARK2 (by changing zconfig.h & compile) would be the next, but I shy away from trying before I have not worked through configuration-only changes. I wonder if there are more touchpoints, known “sweet spots” or similar out there which are configuration only, before I tackle zconfig.h (or other?).

I also wonder if an update to kernel 2.6 (I am running 2.4 from Debian 3.1r0a) could help.

THX in advance!

***** UPDATE *****
This is something that did not occur to me right away: I’ve noticed the following difference following the 1.2.1 update: Before, incoming calls were picked up in the silence following the second ring. Now, incoming calls are picked up during the second ring. If echo cancellation calibrates against the “ring” on the line, it is no surprise it would not work right.
I found this differenc because I still keep a regular phone parallel to the Asterisk box.
I am using my original zapata.conf (carried over from 1.0.9).
I was always wondering how to tune the time/delay for picking up an incoming call, but could not find anything (that made sense (;->).
This is an US installatio. I would not want to go below two full rings in order to allow time for the caller-ID, right?

1.2.1 uses the KB1 echo canceller, unless you change it. IMHO KB1 works better with the 2.6 kernel.

Resolved: I went back to a 10.0.x (10.0.10) zaptel driver. Thankfully it works with Asterisk 1.2.x