If this makes sense, please request it as a sticky, as this will help others.
Error 3007 is related to an issue where your computer is unable to stay connected to the servers. It is not an issue with the game at all, regardless of whether or not you can play steam games, Minecraft, or MW2 online stably, it is absolutely 100% an issue where your computer is unable to stay connected to the server.
In essence, when you get a 3007, it is your computers way of saying "Oh sorry, it seems as though the server is working fine, but I am unable to stay connected to it for some reason".
Now.... this puts it down to two areas that may be causing the problem. Blizzard are often referring people to check their connection within the boundaries of their home. This can relate to a few things:
- Is your modem suitable for online gaming?
- Are you using a decent quality telephone line that has not deteriorated?
- For ADSL adn ADSL2+ users, are you using a line filter with a telephone?
- Do you have any firewalls that may be blocking access (both Windows and third party?
- Are the drivers for your networking cards up to scratch, not corrupted?
- Is your modem near devices that can interfere with the signal (Cordless phones, microwaves, etc)
...and that is just a few things that can go wrong.
For example - I used to get drop outs every single time my phone rang, and the issue was because my cordless phone was not certified to not interfere with a wireless modem. I bought a new handset, and there were no more problems. Ta da!!
Another example - When I first got Diablo III, I used to get the odd occasional 3007 error, which I found was related to my outdated modem that is around 5 years old. I have since replaced it with a Netgear N600 dual band (and had other issues investigated which I will explain later), and it holds solid.
If you have checked your connection within the walls of your home and it seems fine, then it could very well relate to an issue external to your property. In fact, in 90% of cases where people are excessively getting 3007's, you will probably find that this is where the problem is, ESPECIALLY for those here in Australia that have underground cabling. More on that later.
The other part of the connection that regularly fails is the connection between your home and the exchange. Our networks here are mainly copper (except Optus which is Fiber but runs at the same speed as copper), and understandably are extremely outdated and frail. These are the lines that were built at the turn of the century, and are in dire need of replacement (hence the importance of the NBN). These lines fail - especially those that run underground, because of water build up. In some cases, if you open the covers in your street, you will see your cables wrapped up in a Coles shopping bag to protect them from later. Think I'm kidding? I'm not.
This is why, if everything works in your house, I highly recommend talking to your ISP, run through your troubleshooting with them, and then lodge a request for an investigation into the line quality between your home and the exchange. I can promise you that 90% of the 3007 issues that people are experiencing at the moment are a direct result of this.
I also had my lines investigated, and repairs are in progress that have, along with my new modem, already stabilized my connection with the servers for Diablo III.
I know that telling a bunch of people who are upset about the performance of a game that the fault is at their end is never going to be a popular set of words, but frankly, its how it is.
Hope this helps. ;)