I had all the above problems about 6 months after installing 2 MBLs. I spent lots of time and numerous re-boots trying to resolve the problem in addition to all the various ideas in this forum.
Turns out the problem was my 8 port switch connected to my ATT 2Wire 4 port modem. My main network MBL was connected to the ATT 2Wire and the backup MBL to the 8 port. The 8 port went defective and was degrading ONLY the MBL performance over the Network. Everything else worked fine which made it harder to trace. It seemed both MBLs went defective simultaneously - an unlikely 6 sigma occurrence.
Even bypassing the 8 port and connecting both MBLs to the ATT 2Wire did not fix the problem as long as the 8 port was connected the the network.
The problem was resolved in two steps 1) removing the 8 port from the network and 2) blowing it up with 10 pounds of ammonium nitrate and powdered aluminum (aka Tannerite). Step 2 is optional but gratifying.
