You dont tell much about what windows version you use or how you connect... is it dail up connection ?

If regular networking.. look in control panel.. network
maybe off on the left it says something like 'change adaper settings'

on my win7 i might go there and right click one of the two connections.. and disable it. If you can tell which one works and which one doesnt.

What is the operating System? What is the exact error message you receive word for word? Make an model of computer?

How do you connect? wireless using a router? Or a direct connection with a cable?

The first thing to try on these types of issues is to uninstall an reinstall the Network Adapter using Device Manger and see if the resolves it.

you could try a system restore to the date before this happened to see if the problem disappears then you could try the updates again see what happens, I would also check the McAfee forums to see if that is happening to other users. generally if it is there will be lots of people there complaining.

My advice get rid of McAfee, it had my computer so messed up it was horrible, removed McAfee and all of the many problems I had been having vanished, I had no idea that was what was causing all of them. I went with Avast and have been happy happy.
There is a good program that will fully uninstall it for you before putting another AV on so if you choose to do that here it is
Using AppRemover

Sorry to be late getting back to everybody on this, and thanks for your advice! I have a Dell (AMD Phenom) with Vista and a DSL router. I was too busy to deal with the problem last week. And, as long as I leave the computer on, the Internet connection is okay. It's just when I restart it that there's a problem.

I just tried uninstalling and reinstalling the network adapter. But, when I restarted the computer, no Internet. (The error message is the same as you get whenever the computer can't access the Internet.)

The second connection doesn't show up when I first go into the control panel, but pops up a minute or two later. And--as mentioned above--if I disable one, I end up with no connection at all, and have to ask the computer to repair it. Then the Internet will work fine until I try to restart the computer again.

I haven't had difficulties with McAfee before, and don't see this mentioned on their site, so it could just be a coincidence that the problem cropped up right after I installed updates. Any more suggestions?

A few things to try,

Copy and paste the text between the stars below into Notepad.

*********************************************************
@Echo on
pushd\windows\system32\drivers\etc
attrib -h -s -r hosts
echo 127.0.0.1 localhost>HOSTS
attrib +r +h +s hosts
popd
ipconfig /release
ipconfig /renew
ipconfig /flushdns
netsh winsock reset all
netsh int ip reset all
shutdown -r -t 1
del %0
*******************************************************
Now Save as flush.bat to your desktop.
Double-click flush.bat file to run it. Your computer will reboot.

Note: For Windows Vista or Windows 7, right-click flush.bat and select "Run as Administrator"

Next If the above does not work.

Windows 7 and Vista

From the Start menu, select Control Panel, or Settings and then Control Panel.Double-click Network and Sharing Center.

From the list of tasks on the left, click Change adapter settings (in Windows 7), or Manage network connections (in Vista).

For a wired network connection, right-click Local Area Connection, and then select Properties.

For a wireless network connection, right-click Wireless Network Connection, and then select Properties.

From the Networking tab, click Internet Protocol Version 4 (TCP/IPv4), make sure it is checked, and then click Properties.

Click Obtain an IP Address Automatically, and then click OK.

Windows XP

From the Start menu, select Settings, and then Control Panel.

Double-click Network Connections.

For a wired network connection, right-click Local Area Connection, and then select Properties.

For a wireless network connection, right-click Wireless Network Connection, and then select Properties.

From the General tab, click Internet Protocol (TCP/IP), make sure it is checked, and then click Properties.

Click Obtain an IP Address Automatically, and then click OK.

http://uits.iu.edu/page/aiyy

Thanks, Zep516. I tried both of those fixes, but neither worked. Perhaps I'll just have to leave the computer on all the time.

Yeah those fixes were not the best probably for your situation. It almost sounds like a driver or windows Service is not getting loaded at boot time. I'll see if i can find out anything. System file checker might be an idea too.

When yo get time try this and post the logs,

Please download Mini-toolbox and run it. See link.

Checkmark following boxes:

List Winsock Entries
List last 10 Event Viewer log
List Devices (Only Problems)[/list]

Click Go and post the result.

At least here we can have something to look at and may provide a clue for you.

Here is a link that might be useful: http://download.bleepingcomputer.com/farbar/MiniToolBox.exe

Here's how to run System File Checker.

Use the System File Checker tool (SFC.exe) to determine which file is causing the issue, and then replace the file. To do this, follow these steps:

Follow the directions at the link to run System File checker, worth a try and easy to do.

Here is a link that might be useful: System file checker link