We have recently purchased 120 vostro 320 desktops (all in one) we are currently experiencing 40-50 of these machines randomly disconnecting, we have tried forcing the the speed of these nics to 10mbps full duplex and has occasionally worked, but its like the onboard nic has shutdown (No leds are lit up on the back of the pc) a reboot will bring the nic back up to a working state but randomly shuts down again. We have tried turning off all the powersave options for the NIC, and the Bios is the same version as what is listed on the Dell driver support site. We have even tried updating the driver from Realtek but the problem is the same, PXE booting seems to work but also occasionally freezes.
I have also reset bios settings to optimal defaults.
Realtek diagnostic software shows no problems, but there is one other post related to a vostro 320 here http://en.community.dell.com/support-forums/network-internet-wireless/f/3324/p/19302171/19580684.aspx that is showing the exact same symptoms.
Any help would be greatly apreciated.