IP Address conflict? Have you narrowed the MAC down to being a VM in one of your ESX/vSphere clusters? Well use vSphere PowerCLI to figure out what device and adapter is causing the conflict.
Example, if your MAC is 005056b60b13:
Get-vm | Select Name, @{N="Network";E={$_ | Get-networkAdapter | ? {$_.macaddress -eq "00:50:56:b6:0b:13"}}} |Where {$_.Network-ne ""}
And it will output the VM name and the Network Adapter causing the conflict. 🙂