None of my computers can connect to windows update?

Hi, I have 6 computers in the house, 4 running windows 7 and 2 running Windows 8 (Posted in Windows 7 forum as that's where the majority of my PCs are), and none of them are able to connect to windows update. I noticed this today when I finished a clean install of windows on a computer I was fixing for someone else. When I went to check for updates to make sure it had finished fully updating over the past few days (last successful update was on 8/19), I got an error message stating that Windows could not search for new updates (Error 80246002). I looked up this error code though and it seems this error code is mostly related to problems installing updates, not checking for them. I then tried on all of my PCs and none of them can connect either. All of them have a last update check from the last time they were turned on (as early as yesterday 3:25pm). I tried using Microsoft's troubleshooter to see if there are problems but they do not help. Any ideas? I thought it might be my wifi but I checked and there don't seem to be any settings that are off on the router.

These are all computers of varying specifications and program setups, but here's the basics of all of them:

Dell XPS 8300 (Update reports error)
Windows 7 Ultimate
Intel i7 2600
Radeon 6870
8GB RAM
128GB SSD boot drive, 2TB HDD data, several externals as well
Antivirus: AVG Internet Security - tried both enabled and temporarily disabled, no difference

Dell XPS 8300 (PC I am working on, update reports error)
Windows 7 Home Premium
Intel i7 2600
nVidia GT 530
8GB RAM
500GB HDD
Antivirus: McAfee Internet Security

ASUS N53SV (Update just hangs and never finishes checking, most recent updates failed to install)
Windows 8.1 Pro
Intel i7 2670QM
nVidia GT 540m
6GB RAM
256GB SSD
Antivirus: AVG Internet Security

Custom Build - Update reports error
Windows 7 Ultimate (32-bit)
Intel Core 2 Duo T7400
Integrated graphics (945GM I think)
4GB RAM
64GB SSD, 120GB External Data HDD
Antivirus: AVG Free

ASUS EeeBox 1036 - Update hangs
Windows 8.1
Intel Celeron J1900
Intel HD Graphics (Ivy Bridge)
2GB RAM
320GB HDD, 2TB External HDD (Media server)
Antivirus: Norton Internet Security, soon to be AVG Free

For the windows 8 machines, if I let them "update and restart" they take a long time (about 20 minutes for a small update, even on SSD and high performance processor) and eventually report that the update failed and the changes had to be undone. I just don't know what's going on. All of these computers have varying levels of use and varying program setups with almost no common denominators aside from the fact that they all have Windows. One of them is even a completely clean install minus antivirus!