This appears to be a common problem, but I have only recently started to experience it. I have found plenty of suggestions but no satisfactory solution after several hours of research.
I am running a wired ADSL Ethernet connection using a Broadcom Netlink Gigabit network card and a Zyxel 660HW modem. The Internet connection works fine except when I wake the computer from sleep mode. In the past the computer would always reconnect automatically to the Internet after sleep mode, but now it usually does not. I stress “usually” as sometimes the computer DOES reconnect, but more commonly I get a red cross over the connection icon and Vista informs me that the network cable is unplugged (which is rubbish). I can reconnect by doing some or all of the following:
Physically disconnecting and reconnecting the cable
Going to Device Manager, locating the network card and disabling and re-enabling the device
Turning the modem off and on again
This problem never occurs when I shut the computer down fully and restart.
I have tried the following suggestions:
Unchecking the “Allow the computer to turn off...” box in the network card’s Power Management settings
Using a different cable
Running the ipconfig release/renew commands
Setting a different duplex speed
Updating all relevant drivers/firmware/BIOS
Checking in BIOS for sleep mode options (there aren't any)
Restoring the computer to the earliest possible time
The above are the most commonly suggested “fixes” but none of them solves the problem permanently.
I did wonder if the modem or network card is at fault but I experienced wake-up internet connection problems with a Speedtouch USB modem too. I also know other people who are experiencing the same thing with Windows 7.
I write this more in hope than expectation as the problem has been around for a while and seems to come and go without anybody knowing what causes it. Of Vista’s many bugs this is one of the most annoying as sleep mode is a useful facility and I can’t use it while the problem persists. The fact that this problem does not happen every time suggests to me that the sleep/wake cycle is not always functioning as it should – perhaps it has been compromised by a dodgy update.
Any enlightenment gratefully received.