First try adding the game to your whitelist in your Anti-Virus. Don't turn the Anti-virus off, just make sure the game can pass it's checks. If that doesn't work try the following:

For Steam Users

You can also do the same thing inside of steam's launch options:
First find the game in your Steam Library, Click: Manage > Properties > General > Launch Options. Add this command inside the launch options: " -Repair" With the space. Not the quotes. " "

After that you can restart Steam, or just click the "Play" button in your Steam Library. It may take a moment for steam to launch the game. However it should run an Archive Repair by the time it does launch.

I've personally had the best luck with using this method. It forces the game to run the repair every time it launches via steam.

For Windows Users

I found this on their website:[help.guildwars2.com]

If you are running the game on a Windows operating system:

Locate your Gw2.exe file.

Right-click on the file and select Create shortcut.

Rename this new shortcut to Guild Wars 2 Repair.

Right-click on Guild Wars 2 Repair and select Properties.

Locate the Target line and add –repair to the end. (Example: "C:\Games\Guild Wars 2\gw2.exe" -repair)

Click OK.

Now double-click the Guild Wars 2 Repair shortcut. This will begin repairing your game client automatically. The game will then launch when it is complete.

NOTE: Keep in mind that the verification and repair process will run each time you double-click the Guild Wars 2 Repair shortcut; if you would like to play the game without repairing the archive, double-click on Gw2.exe or another shortcut without the -repair command in the 'Target' line.

I understand this is also a hit or miss at times. However I do encourage everyone to leave a comment so others might be able to help out in resolving the issue as well. Even if it's your trouble shooting story. Anything can and may be of use, don't be shy. A pool of information is still a wealth of knowledge.

If there are other methods to fixing this I'm more than happy to add it here. Or to link to a user guild/discussions page you've made. I'd really like for everyone who want's to play, able to play.

Discussions page