When the problem seems to be limited to you (or to your environment) it can really only be diagnosed from your end. If you are using Chrome/Chromium or Firefox with Firebug, you have access to tools that can monitor what's going on. It sounds like most of what you're experiencing at the moment is failed (timed-out) requests (images not loading; scripts not loading). If you're using Chrome, open the Developer Tools and look at the timeline. You may also be able to use a network traffic monitor to see what's happening to the individual requests.
The fact is, though, that if what is happening at your end is only happening at your end, then you have to look at your end. (As for AT&T call center people, well, they get an awful lot of irate people calling them up saying "THE INTERNET IS BROKEN!!!!!". Most of the time, it's a user error or a site experiencing some down time. Their scripts tell them to look in that direction, and it's hard to get them off-script. Most of the time, you'll be talking to someone earning just over minimum wage, not an engineer/tech. You really need to press when you know that what they're telling you is wrong, and you know it's wrong because the whole rest of the world is experiencing no problem.)