We have a whole bunch of 755's that when you select it to boot from
Network card, it comes up saying "Media test failure, check cable". I can
take a 745, 280, 270 and put it on the same cable, and it boots up just
fine. The 755's were working just fine and now they won't. I've even
changed out the cable with no success. I've even tried the boot cd from
IR1, manually loaded the driver, and it will come up to "Network not
Reachable" error.

Any suggestions?