On the 53 VAC ringing, was this what you measured or what the CLEC said was the ringing voltage? Those are FXO ports and I've seen as low as 40 VAC before. I haven't encountered this problem yet on the MP1000. When this locks up, have you clipped on with your butt set at the DMarc and found dial tone or busy out? If the CO lines are locking up, have you tried to release them per instructions on page 29 of the Maintenance manual?? I'm going to play with this on the bench next weekend and adjust the ringing voltage down to see if I can duplicate it. On the MP5000 I haven't upgraded yet to 2.0, but Rather be Fishing might be at hand to answer those issues.