I have an extremely strange network issue occurring when my computer returns from sleep mode.

Every day I leave for work, I lock my station and walk out the door. When I return the next morning, I find my computer has gone into sleep mode (which is fine to save energy), and I simply click the mouse to wake it up. I am then presented with a login screen where I log in. Once I log in, in about 3-5 seconds, everyone in my office loses internet connection, including myself. I get in at various times, 8:00, 8:15, 8:30, 8:45, etc. It never fails, when I get to work, everyone else loses internet access for about 5 minutes or so.

If I have Explorer windows open to any network drives, upon wake, I receive pop-up errors telling me that those resources are not available, however I can quickly go to My Computer and access these drives, so maybe those dialogs are occurring sometime when the computer sleeps and are irrelevant to this issue.

As for our network, well, you can probably think of it as a BIG home network consisted of mostly Windows XP machines, 2 Windows 7 machines and 1 Mac. We really all connect to a big router which is connected to our T1.

This has been happening consistently for the past 2-3 weeks and I can't really think of any software changes I've made that might have done this, however I can't imagine 1 software change I could have made that would take down the internet for everyone on the network, other than a virus of some kind, but it's weird because it only happens for a few minutes, and then everything returns to normal for the rest of the day.

One thing I did notice is one day, Windows installed an update and rebooted my machine during the night. When I returned the next day and logged on, it was a fresh log on, not from sleep, and the internet was not affected then. So it seems to only be happening when I return from sleep mode.

So far, I have taken 2 steps to try to resolve this, but they have not worked.
1. I changed my network from a Work Network, to a Home Network. (I didn't think it would help, but it was worth a shot)
2. Start > My Computer Properties > Device Manager > Network Adapters > Right Click > Properties > Power Management Tab, I have unchecked Allow the computer to turn off this device to save power (which unchecks/disables the 2 boxes below as well)

Has anyone heard of this? It's beginning to irritate my coworkers when this happens every morning.

Ok, so today, I noticed one other thing. I don't actually have to log on for this to occur. Once my computer returns from sleep mode and the login screen is visible, that's when the other computers on the network are affected. I hope that helps in figuring out what could be the problem. I can't find any information about this anywhere.

One thought was maybe when I join the network, something could be wrong with our router and it reboots or something and has to wait for it to reboot before everyone get's new IP addresses. I don't know, just a thought.

Since nobody is responding, I decided the next step was to swap my computer's location on the network with a different port. I swapped places with the #7 port (I'm #31) on our switch. I guess we'll see on Monday if it worked.

Well, changing my network port did not help. Like clockwork, this happened again this morning. I'm not sure what else to do. This is beginning to get very frustrating. Does anyone have any idea how to debug this problem?

It sounds as if you have a conflict of IP numbers - I suggest the ip number for your PC is same as router ?