Sounds like the issue is likely as Chris suggests. The two different standard wiring maps for RJ45 connectors may be the reason you ended up with the wrong pins connected. I would take great care taking the wire colours in an Ethernet cable as the same as pinouts. Either crimp your own plugs or look very carefully at what's connected to each pin at the plug end, presuming you can see it, with shielded connectors you often cannot.

Good luck

Richard

Main system; 861v8 ID41, DSP8000SEU fronts with DSP5500 centre and DSP7000 rears (all in lovely silver) 504, HD621
Second system 861v4 ID40 LPS, G98DH, 504, HD621, 2x DSP5200 with DSP5200 centre
MD600 tucked away in study. Lots of other Meridian!