Thank you for posting in Wired Communities. I am sorry to hear what happened, can you share more information below:
1) What is the exact motherboard or system model the 82579LM embedded on?
2) What is the driver version?
3) Was there any recent changes made on the 5 computers?
4) Does the problem exist if 82579LM wake up from sleep mode?
Have you tried disabling any sleep mode setting in BIOS (in case there is).
Please feel free to update me. Thank you.