Try checking and setting OBi device option 27 to a 1.
See:
http://www.obitalk.com/forum/index.php?topic=2164.0From: RonR
The default is 10mbs/half-duplex.
***0/option 27 reports the current value before allowing you to change it:
0 = 10mbs/half-duplex
1 = 100mbs/full-duplex
It's a total shot in the dark, but you might try changing the OBi Ethernet port from 10mbs/half-duplex to 100mbs/full-duplex:
1. Dial *** 0
2. Enter option 27 and press #
3. Press 1 to set a new value
4. Enter a value of 1 and press #
5. Press 1 to confirm/save
6. Hang up