I run an adhoc wireless network, so my laptop connects through my main PC and shares it's connection, rather than having a proper access point/router. I do this via a USB stick that I can yank when I'm not using the laptop, and don't have the wifi broadcasting hither and yon into the cowfields the other 23 hours I don't use it.
Since installing a few things last week (Finally readding Grisoft's AVG, completely removing and reinstalling the firewall after some major issues of weirdness, Windows updates, etc) when I tried connecting with the laptop, the main PC would spontaneously reboot.
Which while it may be supremely annoying, I actually find kinda cool. "Hey, lookit what I can do from across the room!" After it rebooted with the stick in the USB slot, it seemed to connect fine, but if I tried to reconnect, or pulled the stick, or just came back to it later, again with the reboots. And that's not really the optimum way to get online via the laptop, if it reboots the PC every time.
Tried some uninstalls and reinstalls, and repeated testing over the weekend. Thought I had it once, but I just tried connecting right after it reboot, so was still good I guess. Try searching for wireless network reboots on Google, and have fun. Since most wireless setups require at least a reboot or two to install any software, I didn't get much help there. I'd searched the event log, and didn't find any major problems there I'd not already fixed, or hadn't been around for ages anyways.
Now, this wasn't a unique situation with my computers. This happened awhile back when I installed AOL's free AV program, and it broke something. This was actually when I unstalled AVG, appropriately enough. Something in the program conflicted with the wifi connection and made the computer reboot. Since I knew exactly what I'd done, it was easy enough to uninstall, and that actually fixed the problem back then.
Going out on a limb, I looked, and saw AOL was no longer offering the free antivirus they used to. Knowing the program was basically a skinned version of Kaspersky's, I grabbed theirs, installed it, and surprise...everything worked perfectly. Or so it seemed. Still leery, and not wanting to keep the program JUST for that, I uninstalled it, checked, still good. Waited about an hour and tried again, still good. Yay! Finally slept on it, and about 12 hours later, I just tried again, and finally, everything seems back to what passes for normal on my machine.
I love me some computer voodoo.