Okay, this one is stumping me, and I feel like I'm missing something obvious. Here's the situation:

I have a user who found herself unable to browse the web. Simple enough, I get that a lot. I get to the computer and see a red X over the network icon in the system tray. Okay, I go to see what her adapters are reporting. There are none. The network adapters window is empty. I go to device manager, and there isn't even a category for network adapters.

Okay, weird, but again, I've seen plenty of onboard network adapters go bad, so I figured that's all it was. All I had on hand was a USB wireless adapter, so I set her up with that and was on my way. In the meantime I ordered a PCI Express 1x network adapter card just to have on hand.

I get another call from the user saying she has no internet. I get another cancelling that call because it's back. I get a third cancelling the cancellation because it isn't working again and stays that way. I go out and find the exact same situation, now applying to both adapters.

I open up the computer and go to put the PCIe card in. I then try to turn the computer on and don't even get the POST. I try each slot, and nothing at all happens when I try to turn the machine on. If I remove the card, it boots normally, if I put it in, all I get is fan noise and a little hard drive activity.

So I remove the card and boot up. Now I have the adapters back.

I've scanned for viruses, I've checked event logs, and I've done as much research online as I can think of. I was only able to find a single thread that actually matched the symptoms, but the thread had no resolution (as always seems to be the case...).

Does anyone know what's going on here?