I have been struggling with this issue now for a week. Here's the basics behind things... First of all, the main firewall/DHCP Server/et al for my workplace is a SnapGear SG850. Until recently, everything's been working fine and dandy.
Recently, however, the following problem has arisen.
When going Add a Device or Add a Printer on a Windows 7 machine, or when going into the network to search for a specific computer to attach to (for instance, when looking for another computer to connect to their shared computer), the Windows 7 machine INSTANTLY loses all network connectivity. It retains the assigned IP and whatnot, but you can no longer ping the gateway, DHCP servers, or anything else on the network in any way, shape or form.
The ONLY solution I've found to fix this so far is to log in (from another computer) to the SnapGear SG850 and reboot the router (or, conversely, walk up to it and unplug it). However, this then takes down all the other computers at the same time, resulting in one happy person and 55 unhappy people.
This does NOT occur with a windows XP or earlier machine. While on an XP machine, I'm able to connect to the network neighborhood, surf to any computer on the network (including a win7 machine) and connect to their shared files/printers without any issue at all.
Thoughts? Any help is massively appreciated!