Windows 7 Acer Netbook suddenly won't get on network

First of all, I'm trying to diagnose this problem from 3000 miles away over the phone. I am *very* versed in WinXP, but not at all in Windows 7. As such, I am not looking for a perfect solution at this time, but merely some hints to maybe point me in the right direction, or what the next logical steps in diagnosing this might be.

Brand new Acer D55 with Windows 7 home, bought and configured around Christmas 2010. It was working fine until the middle of April, when suddenly (during usage, i.e., not overnight or after a reset), the Acer dropped off the wireless network while other computers remained on the same wireless network, and continue to remain even now. This is the only Windows 7 computer on that network. All others are XP. Here is where I came in.

I have been troubleshooting remote wireless woes for almost 10 years, and am quite good at it. My first instinct is to have someone plug the computer into the router directly with an Ethernet cable, thus temporarily getting the computer back online long enough for me to VNC in and find out why the computer's wireless connection died. This has ALWAYS worked. I have never seen a computer, that when plugged physically into a functioning router, didn't come online. So as you can probably guess, the computer didn't come online.

The computer has McAfee security installed, and I have seen AV/firewall suites cause problems in computer usage before, but I have never seen one prevent a computer from jumping online.

The biggest concern at this point for me is why the Local Area Connection is failing. But regarding both Local and Wireless connections, here is what I have tried:

- Physically plugging the computer into the router.
- System restoring to 4/16/11, and then again to 3/24/11
- Deleting the stored Wireless connection on record, and adding it back
- ipconfig /release, /renew, various netsh commands

Not knowing anything about Windows 7, and knowing that I am troubleshooting this remotely, can anyone recommend any steps or tests I can run to help me track this down? Or any previous threads or info?

Thanks in advance