This reminds me of a computer tip that a non-computer savvy person will tell their non-computer savvy friends, who then end up calling tech support for a product that doesn't support their home setup, and then the person on the other end has to explain how real-life works (me). 1. Don't rely on an anti-virus program. Your primary defense is a. not being stupid (which is doing things like visiting pron sites, sites with tons of popups, etc), install noscript, and if you must, periodically install anti-virus and run a full scan. 2. Cloud isn't a backup. If you want a backup, spend a little bit of effort. If your stuff is important, back it up yourself. Use your brain and use redundancy if it's actually important to you. 3. Don't let pesky friends use your computer, especially unsupervised. You don't know what kind of sites they are going to visit and what malware they are going to install. 4. Never use system restore. Just backup your stuff, don't install malware (or "Free" programs that want to install themselves with your real programs) and don't follow horrible tips on slashdot (which I would have expected more of)
Are you using wireless or wired? Wireless congestion in your area can saturate the frequency such that you start getting huge packet loss. You might even start connecting a single computer via wire at a time and see if you see the issue with each machine or not.
If you just need your network to work again, you might just consider getting a $5-10 cable off amazon (I'm a sucker for free shipping) or monoprice. You end up with better security, more bandwidth, faster response time, no interference from pesky neighbors, and full duplex. If you have a bunch of computers in one area, you can run one cable to a switch that is by the computers. Of course, you'll still need the wireless eventually for the convenience and mobile devices, but you will probably prefer having a wired network for your desktop machines.