I had a similar issue with my dry loop line. I wasted 2 months talking to the monkey's in tech support, they never believed the connection had any problems. They sent 2 techs to check my wiring (direct to demarc) but the dropouts continued. Their final solution was to put me on the 1.5/384 tier, I cancelled the same day as the line was capable of 5mbit.
Don't let them jerk you around and be prepared to answer the stupid questions about filters, jacks etc every time you talk to the useless level 1 guys. But I found the 'test center' people weren't any better as all they ever did for me was reduce my speed or change me to interleved/fastpath and say the problem was fixed.
I had one test center tech say my connection was fine at 64kbit sync. He kept saying 'it is working though right?' I was like OMFG what morons.
Ironically since the account was closed the loop is still active and it is more stable now than it was during my main problems.
These guys have no understanding of how to troubleshoot dryloop, they can do their 'tests' but they don't do them for 24/48 straight to see if the issue keeps occuring.
Good luck and keep us posted.
BTW here is my thread on my issues, and it is only the main parts of it, Sympatico had 30 tickets on record for sync issues on this line.
»Need help with Sync Issues