[Asterisk-Users] Incoming zap channels busy

[Asterisk]

We have a EuroISDN30, linked directly to * via a TE405P card, on span 3. 
(span 1 is linked to another EuroISDN, and span 2 to a pbx, which we are 
decommissioning).

After a couple of days, I notice that incoming calls are getting more 
and more "busy" tones. These calls are not being handled by * at all - 
there is no messages on the console (verbose 10). After a while, it is 
maybe 1 in 7 calls that make it through to *.

Outgoing calls are still made fine - there are no problems there.

If I stop * and restart, then there are no problems with incoming calls 
for another few days.

I am currently on CVS head (yesterday am) - however this has been going 
on for a few weeks now .

Does anyone have any clues before I really start digging ?

TIA

Julian.