Serial, serial... :(

Having problems with my serial ports at the moment, I think one of the network modules I received last week has a hardware fault. I've tried unbelievable number of combinations, but whether its the DCE, DTE and in multiple different routers, whenever I bring up the port it takes a few seconds and then it throws a "Level 2 Watch Dog Timeout" error and reboots the router.

See exhibit A below :(

I guess you win some and lose some. $55 wasted.