I have a customer that has 9 lines on a bcm50 using the 1230 phones. Every couple of weeks 2 or 3 of the lines get internal echo on them then it goes away. I have gone through all the steps outlined in the echo control papers from Nortel and it works ok, then I get a call a couple weeks later and it will be on 2 different lines. It seems to only happen on phones that have the computer piggy backed through the internal switch. Could that be a problem?