asterisk users - Jul 2005 - X100P/Caller ID: clidtest works, * complains

Hi,

I'm running Asterisk 1.0.8 on Gentoo, with an X100P (clone) card, and 
I'm having problems with Caller ID. I have run clidtest, and it seems 
happy enough, returning:-

server clidtest # ./clidtest /dev/zap/1
Number: 0412222222, Name: MOBILE

(that number's fake.) However, I'm not getting the caller ID passed 
through with *. Sometimes I get a "failed checksum" like this:-

    -- Starting simple switch on 'Zap/1-1'
Jul 30 16:06:14 NOTICE[9597]: callerid.c:306 callerid_feed: Caller*ID 
failed checksum
Jul 30 16:06:15 NOTICE[9597]: chan_zap.c:5405 ss_thread: Got event 2 
(Ring/Answered)...
Jul 30 16:06:16 NOTICE[9597]: chan_zap.c:5405 ss_thread: Got event 2 
(Ring/Answered)...
Jul 30 16:06:18 NOTICE[9597]: chan_zap.c:5405 ss_thread: Got event 2 
(Ring/Answered)...
    -- Executing Wait("Zap/1-1", "2") in new stack
<snip>

and sometimes I get an error that I _really_ don't understand:-

    -- Starting simple switch on 'Zap/1-1'
Jul 30 16:25:02 NOTICE[9616]: chan_zap.c:5405 ss_thread: Got event 2 
(Ring/Answered)...
Jul 30 16:25:02 NOTICE[9616]: chan_zap.c:5405 ss_thread: Got event 2 
(Ring/Answered)...
Jul 30 16:25:04 ERROR[9616]: callerid.c:260 callerid_feed: fsk_serie 
made mylen < 0 (-62)
Jul 30 16:25:04 WARNING[9616]: chan_zap.c:5434 ss_thread: CallerID feed 
failed: Success
Jul 30 16:25:04 WARNING[9616]: chan_zap.c:5476 ss_thread: CallerID 
returned with error on channel 'Zap/1-1'
<snip>

This seems to be a common topic in the archives! I have tried adjusting 
the gain to no avail. This is a Telstra (Australia) CLID service, and I 
have ADSL on the same line (a line filter is installed.) The fact that 
clidtest works suggests that the card's getting the CLID fine, but 
there's a problem after that. Any ideas would be greatly appreciated.

Cheers,

Jon