I have just started work with a company which has the 3750G deployed throughout it's buildings. I am having an issue that is really annoying, some computers are being locked out (red cross for network connectivity icon on sys tray), all the computers that this effects are HP's with a Realtec gig on board card. Now the switches concerned are not managed nor do they have an IP address (I will get round to doing it). The only solution seems to be to replace the card, or reboot the switch (not the most practicle), also most of the computers affected are setup for DHCP(from a server) and most of them aren't even on our domain !!!!. Some but not all when scanned have a fair amount of malware on them. Any suggestions would be appreciated.