asterisk users - Aug 2007 - MOH being activated in the middle of a call

Hi,

I am using Asterisk 1.2.19 and have noticed a strange behaviour in my
system.

Sometimes (I could not reproduce it yet), when there is a call in place
between one extension and a PSTN number, the MOH suddenly starts to play
for one of them, while the other can still hear what is being said in
the conversation. When this issue happens, the call needs to be dropped,
because the MOH plays forever.

Is this a known issue? Any idea about how to solve/avoid it?

Thanks in advance