[Asterisk-Users] no audio on fxo line

[phpmechanic]

Hi,

I got back from two weeks away and appear to have lost audio on my 
tdm411 fxo. Everything was working properly when I left. I checked the 
logs, config files and can't see any problems, the zap channels and 
modules are all loaded properly, asterisk starts without probs and 
everything looks sweet on the colsole with -vvvvvvvvc when I make calls, 
but I just don't hear a dialtone or any audio anymore.  I tried opening 
the sound monitor and that looks as though appropriate sounds are being 
sent.  When I pick up the handset all I can hear is a slight crackling 
noise. The fxo line rings but I don't hear audio through any phones 
connected to it..

I'm not really sure what I can try to resolve this - has anybody got 
some suggetion?